10-Q

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-Q

(Mark One)

☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the quarterly period ended June 30, 2025

OR

☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from ______________ to _______________

Commission File Number: 001-35521

CLEARSIGN TECHNOLOGIES CORPORATION

(Exact name of registrant as specified in its charter)

Delaware
(State or other jurisdiction of
incorporation or organization) 26-2056298
(I.R.S. Employer
Identification No.)

8023 E. 63rd Place, Suite 101

Tulsa, Oklahoma 74133

(Address of principal executive offices)

(Zip Code)

(918) 236-6461

(Registrant’s telephone number, including area code)

Securities registered pursuant to Section 12(b) of the Act:

Title of each class	Trading Symbol(s)	Name of each exchange on which registered
Common Stock	CLIR	The Nasdaq Stock Market LLC

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ⌧ No ☐

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period than the registrant was required to submit such files). Yes ⌧ No ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

Large accelerated filer ☐	Accelerated filer ☐
Non-accelerated filer ⌧	Smaller reporting company ☒
	Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes ☐  No ⌧

As of August 6, 2025, the issuer has 52,426,282 shares of common stock, par value $0.0001, issued and outstanding.

TABLE OF CONTENTS

PART I	FINANCIAL INFORMATION
Item 1.	Financial Statements (unaudited)
	Condensed Consolidated Balance Sheets as of June 30, 2025 and December 31, 2024	1
	Condensed Consolidated Statements of Operations and Comprehensive Loss for the three and six months ended June 30, 2025 and 2024	2
	Condensed Consolidated Statements of Stockholders’ Equity for the three and six months ended June 30, 2025 and 2024	3
	Condensed Consolidated Statements of Cash Flows for the six months ended June 30, 2025 and 2024	5
	Notes to Condensed Consolidated Financial Statements	6
Item 2.	Management’s Discussion and Analysis of Financial Conditions and Results of Operations	18
Item 3.	Quantitative and Qualitative Disclosures About Market Risk	26
Item 4.	Controls and Procedures	26
PART II	OTHER INFORMATION	27
Item 1.	Legal Proceedings	27
Item 1A.	Risk Factors	27
Item 2.	Unregistered Sales of Equity Securities and Use of Proceeds	28
Item 3.	Defaults Upon Senior Securities	28
Item 4.	Mine Safety Disclosures	28
Item 5.	Other Information	28
Item 6.	Exhibits	29
	SIGNATURES	31

PART I - FINANCIAL INFORMATION

ITEM 1. FINANCIAL STATEMENTS

ClearSign Technologies Corporation and Subsidiary

Condensed Consolidated Balance Sheets

(Unaudited)

(in thousands, except share and per share data)	June 30,		December 31,
	2025		2024
ASSETS
Current Assets:
Cash and cash equivalents	$	12,339	$	14,035
Accounts receivable		25		165
Contract assets		268		194
Prepaid expenses and other assets		550		454
Total current assets		13,182		14,848
Fixed assets, net		251		238
Patents and other intangible assets, net		798		830
Total Assets	$	14,231	$	15,916
LIABILITIES AND STOCKHOLDERS' EQUITY
Current Liabilities:
Accounts payable and accrued liabilities	$	1,556	$	1,220
Current portion of lease liabilities		93		75
Accrued compensation and related taxes		378		671
Contract liabilities		1,675		73
Total current liabilities		3,702		2,039
Long Term Liabilities:
Long term lease liabilities		115		113
Total liabilities		3,817		2,152
Commitments and contingencies (Note 9)
Stockholders’ Equity:
Preferred stock, $0.0001 par value, 2,000,000 shares authorized, no shares issued or outstanding		—		—
Common stock, $0.0001 par value, 87,500,000 shares authorized, 52,426,282 and 50,285,509 shares issued and outstanding at June 30, 2025 and December 31, 2024, respectively.		5		5
Additional paid-in capital		113,202		112,796
Accumulated other comprehensive loss		(21)		(21)
Accumulated deficit		(102,772)		(99,016)
Total stockholders' equity		10,414		13,764
	$	14,231	$	15,916

The accompanying notes are an integral part of these unaudited condensed consolidated financial statements.

1

ClearSign Technologies Corporation and Subsidiary

Condensed Consolidated Statements of Operations and Comprehensive Loss

(Unaudited)

(in thousands, except share and per share data)	For the Three Months Ended				For the Six Months Ended
	June 30,				June 30,
	2025		2024		2025		2024
Revenues	$	133	$	45	$	534	$	1,147
Cost of goods sold		78		3		283		668
Gross profit		55		42		251		479
Operating expenses:
Research and development		247		402		694		683
General and administrative		1,646		1,777		3,652		3,185
Total operating expenses		1,893		2,179		4,346		3,868
Loss from operations		(1,838)		(2,137)		(4,095)		(3,389)
Other income, net:
Interest income		115		77		248		138
Government assistance		43		185		91		264
Other income, net		—		3		—		7
Total other income, net		158		265		339		409
Net loss	$	(1,680)	$	(1,872)	$	(3,756)	$	(2,980)
Net loss per share - basic and fully diluted	$	(0.03)	$	(0.04)	$	(0.07)	$	(0.07)
Weighted average number of shares outstanding - basic and fully diluted		55,217,968		47,312,810		55,107,588		43,080,454
Comprehensive loss:
Net loss	$	(1,680)	$	(1,872)	$	(3,756)	$	(2,980)
Foreign-exchange translation adjustments		—		(1)		—		(4)
Comprehensive loss	$	(1,680)	$	(1,873)	$	(3,756)	$	(2,984)

The accompanying notes are an integral part of these unaudited condensed consolidated financial statements.

2

ClearSign Technologies Corporation and Subsidiary

Condensed Consolidated Statements of Stockholders’ Equity

For the Three Month Periods During the Six Months Ended June 30, 2025 and 2024

(Unaudited)

						Accumulated Other				Total
(in thousands, except per share data)	Common Stock			Additional		Comprehensive		Accumulated		Stockholders’
	Shares	Amount		Paid-In Capital			Loss	Deficit		Equity
Balances at December 31, 2024	50,286	$	5	$	112,796	$	(21)	$	(99,016)	$	13,764
Share-based compensation, net of tax withholdings	81		—		45		—		—		45
Fair value of stock issued in payment of accrued compensation	326		—		279		—		—		279
Shares issued for services	4		—		4		—		—		4
Exercise of warrants	23		—		24		—		—		24
Exercise of prefunded warrants	1,703		—		—		—		—		—
Net loss	—		—		—		—		(2,076)		(2,076)
Balances at March 31, 2025	52,423		5		113,148		(21)		(101,092)		12,040
Share-based compensation, net of tax withholdings	—		—		51		—		—		51
Shares issued for services	3		—		3		—		—		3
Net loss	—		—		—		—		(1,680)		(1,680)
Balances at June 30, 2025	52,426	$	5	$	113,202	$	(21)	$	(102,772)	$	10,414

3

ClearSign Technologies Corporation and Subsidiary

Condensed Consolidated Statements of Stockholders’ Equity

For the Three Month Periods During the Six Months Ended June 30, 2025 and 2024

(Unaudited)

						Accumulated Other				Total
(in thousands, except per share data)	Common Stock			Additional		Comprehensive		Accumulated		Stockholders'
	Shares	Amount		Paid-In Capital			Loss	Deficit		Equity
Balances at December 31, 2023	38,687	$	4	$	98,922	$	(17)	$	(93,717)	$	5,192
Share-based compensation	67		—		67		—		—		67
Tax withholdings related to share-based compensation	(22)		—		(16)		—		—		(16)
Fair value of stock issued in payment of accrued compensation	307		—		326		—		—		326
Shares issued for services ($0.81 per share)	4		—		3		—		—		3
Foreign-exchange translation adjustment	—		—		—		(3)		—		(3)
Net loss	—		—		—		—		(1,108)		(1,108)
Balances at March 31, 2024	39,043		4		99,302		(20)		(94,825)		4,461
Share-based compensation	256		—		344		—		—		344
Tax withholdings related to share-based compensation	(11)		—		(13)		—		—		(13)
Shares issued for services ($0.81 per share)	4		—		3		—		—		3
Issuance of common stock in public offering, net of expenses	5,314		1		2,390		—		—		2,391
Issuance of warrants in public offering, net of expenses	—		—		1,831		—		—		1,831
Issuance of common stock in private placement, net of expenses	2,250		—		865		—		—		865
Issuance of prefunded warrants in private placement, net of expenses	—		—		1,214		—		—		1,214
Issuance of warrants in private placement, net of expenses	—		—		2,389		—		—		2,389
Issuance of common stock for participation right exercise, net of expenses	3,350		—		1,447		—		—		1,447
Issuance of prefunded warrants for participation right exercise, net of expenses	—		—		580		—		—		580
Issuance of warrants for participation right exercise, net of expenses	—		—		2,250		—		—		2,250
Foreign-exchange translation adjustment	—		—		—		(1)		—		(1)
Net loss	—		—		—		—		(1,872)		(1,872)
Balances at June 30, 2024	50,206	$	5	$	112,602	$	(21)	$	(96,697)	$	15,889

The accompanying notes are an integral part of these unaudited condensed consolidated financial statements.

4

ClearSign Technologies Corporation and Subsidiary

Condensed Consolidated Statements of Cash Flows

(Unaudited)

(in thousands)	For the Six Months Ended June 30,
	2025		2024
Cash flows from operating activities:
Net loss	$	(3,756)	$	(2,980)
Adjustments to reconcile net loss to net cash used in operating activities:
Common stock issued for services		7		6
Share-based compensation, net of tax withholdings		96		382
Depreciation and amortization		98		91
Right-of-use asset amortization		44		43
Lease amendments		—		(3)
Change in operating assets and liabilities:
Contract assets		(75)		183
Accounts receivable		140		152
Prepaid expenses and other assets		(96)		(238)
Accounts payable, accrued liabilities, and lease liabilities		330		78
Accrued compensation and related taxes		(13)		52
Contract liabilities		1,603		(291)
Net cash used in operating activities		(1,622)		(2,525)
Cash flows from investing activities:
Acquisition of fixed assets		(4)		(18)
Disbursements for patents and other intangible assets		(53)		(99)
Net cash used in investing activities		(57)		(117)
Cash flows from financing activities:
Proceeds from issuance of common stock, net of offering costs		—		12,967
Proceeds from exercise of warrants		24		—
Taxes paid related to vesting of restricted stock units		(41)		(31)
Net cash provided by (used in) financing activities		(17)		12,936
Effect of exchange rate changes on cash and cash equivalents		—		(4)
Net change in cash and cash equivalents		(1,696)		10,290
Cash and cash equivalents, beginning of period		14,035		5,684
Cash and cash equivalents, end of period	$	12,339	$	15,974
Supplemental disclosure of cash flow information:
Officer and employee equity awards for prior year accrued compensation	$	279	$	326
Non-cash impact of new lease	$	68	$	32

The accompanying notes are an integral part of these unaudited condensed consolidated financial statements.

5

ClearSign Technologies Corporation

Notes to Unaudited Condensed Consolidated Financial Statements

Note 1 – Organization and Description of Business

ClearSign Technologies Corporation (“ClearSign” or the “Company”) designs and develops products and technologies for the purpose of decarbonization and improving key performance characteristics of industrial and commercial systems, including operational performance, energy efficiency, emission reduction, safety, and overall cost-effectiveness. The Company’s patented technologies are designed to be embedded in established original equipment manufacturers (“OEM”) products as ClearSign Core™ and ClearSign Eye and other sensing configurations in order to enhance the performance of combustion systems and fuel safety systems in a broad range of markets. These markets include energy (upstream oil production and down-stream refining), commercial/industrial boiler, chemical, petrochemical, transport and power industries. The Company’s primary technology is its ClearSign Core™ technology, which achieves very low emissions without the need of selective catalytic reduction.

The Company was originally incorporated in the State of Washington in 2008. During January 2022, the Company relocated its headquarters from Seattle, Washington to Tulsa, Oklahoma. Effective June 15, 2023, the Company changed its state of incorporation to Delaware. On July 28, 2017, the Company incorporated a subsidiary, ClearSign Asia Limited, in Hong Kong to represent the Company’s business and technological interests throughout Asia. Through ClearSign Asia Limited, the Company has established a wholly foreign owned enterprise in China – ClearSign Combustion (Beijing) Environmental Technologies Co., LTD. On August 22, 2024, the Company’s Board of Directors (the “Board”) authorized management to move forward with filing for dormancy with Chinese regulators to suspend the Company’s Beijing, China operations. A dormancy filing allows the Company to keep its China legal entity in a suspended status for up to three years. The Company can revive its China operations at any time during those three years with minimal cost impact. The effective date of our dormancy filing was March 12, 2025.

Unless otherwise stated or the context otherwise requires, the terms “we,” “us,” “our,” “ClearSign” and the “Company” refer to ClearSign Technologies Corporation and its subsidiary, ClearSign Asia Limited.

Business Segments

The Company operates in one operating and reportable segment engaged in the design, development and sale of combustion technologies that improve the performance and cost-effectiveness of industrial combustion systems, referred to herein as the “Combustion” segment. The Company manages its business activities on a consolidated basis. Since the operations comprise a single reportable segment, amounts reported in the consolidated balance sheets, statements of operations and comprehensive loss, stockholders’ equity, and cash flows represent the activities of the Combustion segment.

The Combustion segment derives revenues by delivering products and technology solutions to OEM’s and end-users. Our products and solutions can be incorporated into a new or existing customer infrastructure or equipment. Customer contracts can include multiple billing milestones and performance obligations. The Company can typically satisfy its performance obligations within a twelve month period, but customer project delays, some of which can be beyond the Company’s control, can impact timing of performance and there is no assurance we will satisfy all performance obligations in such period of time.

The Company’s Chief Executive Officer, who is the chief operating decision maker (“CODM”), reviews quarterly financial information on a consolidated basis for making operating decisions, allocating resources and evaluating financial performance. The CODM consistently reviews the consolidated statements of operations and comprehensive loss to manage operations and monitor performance against management expectations. Factors considered by the CODM when assessing a reportable segment include factors such as, but not limited to, human capital, intellectual property, customer relationships and business model design.

6

Substantially all the Company’s operating activities, including its long-lived assets, are located within the United States. Customers in the United States accounted for 100% of revenues during the three and six months ended June 30, 2025 and 2024. The Company disaggregates geographical revenues by selling location, since many of our target customers are global entities, and it would be more likely than not, that these customers would negotiate sales within our current territory in the United States.

Note 2 – Summary of Significant Accounting Policies

Basis of Presentation

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the “SEC”) for reporting on Form 10-Q. Accordingly, certain information and footnote disclosures normally included in financial statements prepared in accordance with generally accepted accounting principles have been condensed or omitted pursuant to such rules and regulations. The condensed consolidated balance sheet at December 31, 2024 has been derived from the Company’s audited consolidated financial statements as of that date.

In the opinion of management, these condensed consolidated financial statements reflect all normal recurring and other adjustments necessary for a fair presentation. These condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2024. Operating results for interim periods are not necessarily indicative of operating results for an entire fiscal year or any other future periods.

The accompanying unaudited condensed consolidated financial statements include the accounts of ClearSign and its subsidiary. Intercompany balances and transactions have been eliminated in consolidation.

Use of Estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make certain estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Research and Development

The cost of research and development is expensed as incurred. Research and development costs consist of salaries, benefits, share-based compensation, consumables, and consulting fees, including costs to develop and test prototype equipment and parts. Research and development costs have been offset by funds received, if any, from strategic partners in cost sharing, collaborative projects. During the three and six months ended June 30, 2025, the Company received no funds from these types of arrangements. During the three and six months ended June 30, 2024, the Company received zero and $107 thousand, respectively, from these types of arrangements.

Foreign Operations

The accompanying unaudited condensed consolidated balance sheets as of June 30, 2025 and December 31, 2024 include assets amounting to approximately $170 thousand and $145 thousand, respectively, relating to the operations of ClearSign Asia Limited. The Beijing registered capital requirement is $350 thousand, which is required to be paid by June 30, 2032, and of which $211 thousand has been paid as of June 30, 2025. On August 22, 2024, the Board authorized management to move forward with filing for dormancy with Chinese regulators to suspend the Company’s Beijing, China operations. A dormancy filing allows the Company to keep its China legal entity in a suspended status for up to three years. The Company can revive its China operations at any time during those three years with minimal cost impact. The dormancy filing became effective as of March 12, 2025.

7

Recently Issued Accounting Pronouncements

In December 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures (“ASU 2023-09”) to enhance the transparency and decision-making usefulness of income tax disclosures by requiring additional information on an entity's tax rate reconciliation, as well as income taxes paid. ASU 2023-09 is effective for our reporting period beginning January 1, 2025. We are currently assessing the impact that the adoption of ASU 2023-09 will have on the disclosures in our annual consolidated financial statements.

In November 2024, FASB issued ASU No. 2024-03, Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40) (“ASU 2024-03”). ASU 2024-03 requires enhanced disclosures about types of expenses, including purchases of inventory, employee compensation, depreciation, and amortization, in commonly presented expense captions. The amendments are effective for fiscal years beginning after December 15, 2026, and interim periods beginning after December 15, 2027, with early adoption permitted. Entities may apply the amendments prospectively or retrospectively to any or all prior periods presented in the financial statements. We are currently evaluating the impact that this guidance will have on the disclosures within our consolidated financial statements. While ASU 2024-03 will impact only our disclosures and not our financial condition and results of operations, we are assessing when we will adopt the ASU 2024-03.

In May 2025, FASB issued ASU No. 2025-04, Compensation—Stock Compensation (Topic 718) and Revenue from Contracts with Customers (Topic 606): Clarifications to Share-Based Consideration Payable to a Customer (“ASU 2025-04”), which clarifies the guidance on the accounting for share-based payment awards that are granted by an entity as consideration payable to its customer, with the intent to reduce diversity in practice and improve existing guidance by revising the definition of a “performance condition” and eliminating a forfeiture policy election for service conditions associated with share-based consideration payable to a customer. ASU 2025-04 also clarifies the guidance in Topic 606 on the variable consideration constraint does not apply to share-based consideration payable to a customer “regardless of whether an award’s grant date has occurred.” ASU 2025-04 is effective for our reporting period beginning January 1, 2027, with early adoption permitted.  We are currently assessing the impact that the adoption of ASU 2025-04 will have on the disclosures in our annual consolidated financial statements.

Note 3 – Fixed Assets, Net

Fixed Assets, Net

Fixed assets, net are summarized as follows:

	June 30,		December 31,
(in thousands)	2025		2024
Office furniture and equipment	$	103	$	99
Leasehold improvements		43		43
		146		142
Accumulated depreciation and amortization		(97)		(85)
		49		57
Operating lease ROU assets, net		202		181
Total	$	251	$	238

Depreciation expense for the three and six months ended June 30, 2025 was $7 thousand and $12 thousand, respectively.

Depreciation expense for the three and six months ended June 30, 2024 was $4 thousand and $11 thousand, respectively.

8

Leases

The Company leases office space in Tulsa, Oklahoma, Seattle, Washington, and Beijing, China. During May 2025, the Company renewed its Beijing, China lease for 24 months with monthly rent at approximately $3 thousand. As a result of this renewal, the Company increased the right-of-use (“ROU”) asset and lease liability by $68 thousand during the six months ended June 30, 2025.

During October 2024, the Company entered into a sub-lease agreement to rent office space in Seattle for approximately $2 thousand per month for twelve months. The Seattle lease is considered a short-term lease, as the lease term is 12 months or less from the commencement date. The short-term lease expense for the three and six months ended June 30, 2025 was approximately $5 thousand and $11 thousand, respectively. The short-term lease expense for the three and six months ended June 30, 2024 was approximately $5 thousand and $11 thousand, respectively. The Tulsa and Beijing leases are classified as operating leases, with remaining terms ranging from two years to approximately three years; contractual language requires renewal negotiations to occur at or near termination. These leases are normal and customary for office space, in that, contractual guarantees exist requiring the lessee return the premises to its original functional state.

The Tulsa lease contains fixed annual lease payments that increase annually by 2%. The Seattle, Tulsa, and Beijing total monthly minimum rent is approximately $10 thousand, in the aggregate. Operating lease costs for the three and six months ended June 30, 2025 was $25 thousand and $49 thousand, respectively. Operating lease costs for the three and six months ended June 30, 2024 was $24 thousand and $48 thousand, respectively.

Supplemental balance sheet information related to operating leases is as follows:

		June 30,			December 31,
(in thousands)		2025			2024
Operating lease ROU assets, net	$	202		$	181
Lease Liabilities:
Current lease liabilities	$	93		$	75
Long term lease liabilities		115			113
Total lease liabilities	$	208		$	188
Weighted average remaining lease term (in years):		2.2			2.6
Weighted average discount rate:		4.4	%		5.3	%

Supplemental cash flow information related to operating leases is as follows:

	For the Six Months Ended
	June 30,
(in thousands)		2025		2024
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows used in operating leases	$	49	$	49
Non-cash impact of new leases and lease modifications
Change in operating lease liabilities	$	68	$	29
Change in operating lease ROU assets	$	68	$	32

9

Minimum future payments under the Company’s operating lease liabilities as of June 30, 2025 are as follows:

(in thousands)
2025 (remaining)	$	50
2026		101
2027		68
Total future lease payments		219
Less: imputed interest		(11)
	$	208

Note 4 – Patents and Other Intangible Assets

Patents and other intangible assets are summarized as follows:

	June 30,		December 31,
(in thousands)	2025		2024
Patents
Patents pending	$	377	$	346
Issued patents		1,056		1,034
		1,433		1,380
Trademarks
Registered trademarks		86		86
		86		86
Other		8		8
		1,527		1,474
Accumulated amortization		(729)		(644)
	$	798	$	830

Amortization expense for three and six months ended June 30, 2025 was $43 thousand and $85 thousand, respectively.

Amortization expense for three and six months ended June 30, 2024 was $42 thousand and $80 thousand, respectively.

Future amortization expense associated with issued patents and registered trademarks as of June 30, 2025 is as follows:

(in thousands)
2025 (remaining)	$	75
2026		130
2027		106
2028		70
2029		30
Thereafter		2
	$	413

The amortization life for patents ranges between three to five years and trademark lives are set at ten years. The Company does not amortize patents or trademarks classified as pending.

During the three and six months ended June 30, 2025 and 2024, the Company assessed its patent and trademark assets. The Company also evaluated its strategic approach to the pursuit and protection of its intellectual property. It is the

10

intent of the Company to continue to pursue intellectual property protection. If the Company identifies certain assets where the intellectual property does not directly align with its core technology, the Company will impair the intangible asset and write-off the asset as an expense.

Note 5 – Revenue, Contract Assets and Contract Liabilities

The Company’s contracts with customers generally have performance obligations and a schedule of non-refundable cancellation obligations. Performance obligations typically fall into one of three categories, product shipment, burner performance tests and engineering design. Customer payment milestones are unique to individual contracts and may occur prior to completion of performance obligations. Customer payment terms typically range between thirty and sixty days from the date of billing. Our customer contracts typically have a duration of less than twelve months. Delays in contract performance, if any, typically occur as a result of customer onsite project delays outside of our control.

The Company recognized $133 thousand of revenues and $78 thousand of cost of goods sold during the three months ended June 30, 2025. The revenue and cost of goods sold relate to spare parts orders from multiple customers, and delivery of a boiler burner to a repeat customer. These products and services constitute performance obligations.

The Company recognized $534 thousand of revenues and $283 thousand of cost of goods sold during the six months ended June 30, 2025. The revenue and cost of goods sold predominantly relate to spare parts orders for multiple customers, sales of boiler burners to a single customer, and the successful completion of an engineering study referred herein as a Computational Fluid Dynamic analysis (“CFD”). These products and services constitute performance obligations.

The Company recognized $45 thousand of revenues and $3 thousand of cost of goods sold during the three months ended June 30, 2024. The revenue and cost of goods sold relate to the successful completion of engineering studies for a repeat customer. These products and services constitute performance obligations.

The Company recognized $1,147 thousand of revenues and $668 thousand of cost of goods sold during the six months ended June 30, 2024. The revenue and cost of goods sold relate predominantly to the Company’s process burner product line. The Company delivered multiple burners in connection with a single customer order, successfully completed engineering studies and a CFD analysis, and fulfilled multiple spare parts orders. These products and services constitute performance obligations.

The Company had contract assets of $268 thousand and $194 thousand at June 30, 2025 and December 31, 2024, respectively. The Company had contract liabilities of $1,675 thousand and $73 thousand at June 30, 2025 and December 31, 2024, respectively. Of the $73 thousand contract liabilities balance at December 31, 2024, the Company recognized revenue of $10 thousand and $33 thousand during the three and six months ended June 30, 2025, respectively.

Note 6 – Product Warranties

A summary of the Company’s warranty liability activity, which is included in accounts payable and accrued liabilities in the accompanying condensed consolidated balance sheets as of June 30, 2025 and December 31, 2024, is as follows:

	June 30,		December 31,
(in thousands)	2025		2024
Warranty liability at beginning of year	$	471	$	110
Accruals		46		478
Payments		(162)		(114)
Changes related to expirations and settlements		(24)		(3)
Warranty liability at end of period	$	331	$	471

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Note 7 – Equity

Common Stock and Preferred Stock

The Company is authorized to issue 87.5 million shares of common stock and 2.0 million shares of preferred stock. Preferences, limitations, voting powers and relative rights of any preferred stock to be issued may be determined by the Board. The Company has not issued any shares of preferred stock.

The Company has an At-The-Market (“ATM”) program pursuant to an ATM Offering Agreement with H.C. Wainwright & Co., LLC (“Wainwright”) as sales agent, dated July 17, 2025 (the “Sales Agreement”), pursuant to which the Company may sell shares of common stock with an aggregate offering price of up to $10.39 million. We previously had an ATM program with Virtu Americas LLC (the “Virtu ATM”), which was terminated effective as of July 12, 2025. As of June 30, 2025, we cumulatively issued approximately 1.6 million shares of common stock under the Virtu ATM, at an average price of $3.84 per share. Gross proceeds totaled approximately $6.1 million and net cash proceeds was approximately $5.9 million.

The Company is currently subject to the SEC’s “baby shelf rules,” which prohibit companies with a public float of less than $75 million from issuing securities under a shelf registration statement in excess of one-third of such company’s public float in a 12-month period. These rules may limit future issuances of shares by the Company under our “shelf” registration statement on Form S-3, including through the ATM program with Wainwright or other securities offerings.

Warrants and Pre-Funded Warrants 

The following table summarizes the activity and outstanding balance of our outstanding warrants and pre-funded warrants as of June 30, 2025, along with the associated weighted average exercise price and weighted average remaining life for such warrants and pre-funded warrants.  

	Warrants						Pre-Funded Warrants(1)
(in thousands, except per share data)	Number		Wtd. Avg. Exercise Price	Wtd. Avg. Remaining Life (in years)		Aggregate Intrinsic Value	Number		Wtd. Avg. Exercise Price		Aggregate Intrinsic Value
Beginning Balance	21,295	$	1.0535	4.74	$	8,230	4,499	$	0.0001	$	6,478
Granted	—		—				—		—
Exercised	(23)		1.0500				(1,703)		0.0001
Forfeited/Expired	—		—				—		—
Outstanding at Period End	21,272	$	1.0535	4.24	$	—	2,796	$	0.0001	$	1,565
(1) Pre-funded warrants have no expiration date and only expire when exercised in full.

Refer to the Company’s Annual Report on Form 10-K for the year ended December 31, 2024 for details related to our outstanding warrants and pre-funded warrants.

Equity Incentive Plan

On June 17, 2021, the Company's stockholders approved and the Company adopted the ClearSign Technologies Corporation 2021 Equity Incentive Plan (the “2021 Plan”) which permits the Company to grant incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock, restricted stock units, performance units, and performance shares, to eligible participants, which includes employees, directors and consultants. The Board’s Human Capital and Compensation Committee (the “Compensation Committee”) is authorized to administer the 2021 Plan.

The 2021 Plan provides for an annual increase in available shares equal to the lesser of (i) 10% of the aggregate number of shares of common stock issued by the Company in the prior fiscal year; or (ii) such number provided by the

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Compensation Committee; provided, however, that the total cumulative increase in the number of shares available for issuance pursuant to this automatic share increase shall not exceed 400 thousand shares of common stock. In 2025, the Board did not exercise their right to limit the automatic increase. Accordingly, the 2021 Plan share reserve increased by 400 thousand shares.

Ending balances for the 2021 Plan is as follows:

	June 30,	December 31,
(in thousands)	2025	2024
Outstanding options and restricted stock units	3,474	3,316
Reserved but unissued shares under the Plan	1,692	1,858
Reserved but unissued shares at end of period	5,166	5,174

Stock Options

Under the terms of the 2021 Plan, incentive stock options and nonstatutory stock options must have an exercise price at or above the fair market value on the date of the grant. At the time of grant, the Company will determine the period within which the option may be exercised and will specify any conditions that must be satisfied before the option vests and may be exercised. The Company estimates the fair value of stock options on the date of grant using the Black-Scholes option pricing model.

As permitted by SEC Staff Accounting Bulletin 107, management utilized the simplified approach to estimate the expected term of the options, which represents the period of time that options granted are expected to be outstanding. Expected volatility has been determined through the Company’s historical stock price volatility. The Company has not made an estimate of forfeitures at the time of the grant, but rather accounts for forfeitures at the time they occur. The risk-free rate for periods within the expected life of the option is based on the U.S. Treasury yield in effect at the time of grant. The Company has never declared or paid dividends and has no plans to do so in the foreseeable future.

Equity Incentive Plan Options

Compensation expense associated with stock option awards for the three and six months ended June 30, 2025 totaled $17 thousand and $38 thousand, respectively. Compensation expense associated with stock option awards for the three and six months ended June 30, 2024 totaled $28 thousand and $50 thousand, respectively.

A summary of the Company’s 2011 Equity Incentive Plan and the 2021 Plan stock option activity and changes is as follows:

	June 30,
	2025
(in thousands, except per share data)	Options to Purchase Common Stock	Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value
Outstanding at beginning of year	2,452	$	2.04	4.92	$	496
Granted	—	$	—
Exercised	—	$	—
Forfeited/Expired	(55)	$	2.56
Outstanding at end of period	2,397	$	2.03	4.18	$	—
Exercisable at end of period	1,872	$	1.70	3.78	$	—

The intrinsic value is the difference between the Company’s common stock price and the option exercise prices multiplied by the number of in-the-money options. This amount changes based on the fair value of the Company’s common stock.

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At June 30, 2025, there was $249 thousand of total unrecognized compensation cost related to non-vested stock option-based compensation arrangements. Vesting criteria ranges from time-based to performance-based. The Company records costs for time-based arrangements ratably across the timeframe, whereas performance-based arrangements require management to continually evaluate predetermined goals against actual circumstances. The maximum contractual term for these options are ten years from the grant date.

Inducement Options

During the year ended December 31, 2023, the Company granted non-qualified stock options to its Chief Technology Officer to purchase an aggregate of 150 thousand shares of common stock with an exercise price of $0.91 as a material inducement to accept employment with the Company. These inducement options vest in three equal installments, with one third of the option vesting on the grant date, and each remaining third vesting on the second and third anniversaries of the grant date, subject to continued employment with the Company. The fair value of these options were estimated on the grant date using the Black-Scholes valuation model, which resulted in $112 thousand. The compensation expense recognized for these awards for the three and six months ended June 30, 2025 was $9 thousand and $18 thousand, respectively. The compensation expense recognized for these awards for the three and six months ended June 30, 2024 was $10 thousand and $19 thousand, respectively. Total unrecognized compensation expense for these inducement options as of June 30, 2025 was $13 thousand.

These inducement options were granted outside of the 2021 Plan and in accordance with the employment inducement

exemption provided under Nasdaq Listing Rule 5635(c)(4).

A summary of the Company’s inducement option activity and changes is as follows:

	June 30,
	2025
(in thousands, except per share data)	Options to Purchase Common Stock	Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value
Outstanding at beginning of year	491	$	1.53	3.04	$	119
Granted	—	$	—
Exercised	—	$	—
Forfeited/Expired	—	$	—
Outstanding at end of period	491	$	1.53	2.55	$	—
Exercisable at end of period	441	$	1.60	2.79	$	—

Restricted Stock Units

The Company awards employees and directors restricted stock units (“RSUs”) in lieu of cash payment for compensation. These awards are granted from the 2021 Plan. Employee vesting criteria is time based, and compensation expense is recognized ratably across the timeframe. The Company pays payroll withholding taxes on behalf of the employee at vesting, and withholds shares from the employee’s award to cover the taxes payable. The Company accrued taxes for RSU share-based compensation of $18 thousand and $29 thousand for the six months ended June 30, 2025 and 2024, respectively. Total unrecognized compensation expense for employee RSUs as of June 30, 2025 was $266 thousand.

Director vesting criteria is contingent upon the occurrence of one of four future events, which the Company cannot predict or control. Therefore, compensation expense for director RSUs is not recognized until one of these four future events occur, which is in accordance with FASB Accounting Standards Codification (“ASC”) Topic 718, “Compensation – Stock Compensation.” Total unrecognized compensation expense for director services as of June 30, 2025 was $743 thousand. Director compensation is earned on a quarterly basis with the target value of compensation set at approximately $75 thousand per quarter, assuming five directors, one chairperson for each committee and two committee members for each of the three committees. As of June 30, 2025, we had seven directors.

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On May 27, 2025, David M. Maley notified the Company that he would not stand for re-election as a director of the Company upon the expiration of his current term, which expired at the Company’s 2025 annual meeting of stockholders held on July 25, 2025. In addition, Judith S. Schrecker and Catharine M. de Lacy both resigned from the Board and its committees effective as of August 4, 2025.

A summary of the Company’s RSUs activity is as follows:

	June 30,
	2025
(in thousands, except per share data)	Number of Shares	Weighted Average Grant Date Fair Value		Weighted Average Contractual Life (in years) (1)
Nonvested at beginning of year	865	$	0.99	0.88
Granted	393	$	0.91
Vested	(121)	$	0.91
Forfeited	(60)	$	0.92
Nonvested at end of period	1,077	$	0.97	1.36

1) The weighted average contractual life calculation excludes the number of director RSUs that vest upon one of four performance events (refer to discussion above for details).

A summary of the Company’s RSU compensation expense is as follows:

	For the Three Months Ended				For the Six Months Ended
	June 30,				June 30,
(in thousands, except per share data)	2025		2024		2025			2024
Share-based compensation expense	$	34	$	306	$	66	$	342
Weighted average value per share	$	0.89	$	1.36	$	0.89	$	1.32

Stock Awards

The Company awards employees stock in lieu of cash payment for compensation, typically to satisfy accrued bonus compensation. The awards are granted from the 2021 Plan.

	2025					2024
(in thousands, except per share data)	Number of Shares	Fair Value		Weighted Average per Share		Number of Shares	Fair Value		Weighted Average per Share
Fair value of stock payments in accrued compensation	326	$	279	$	0.85	307	$	326	$	1.06

Consultant Stock Plan

The Company’s 2013 Consultant Stock Plan (the “Consultant Plan”) provides for the granting of shares of common stock to consultants who provide services related to capital raising, investor relations, and making a market in or promoting the Company’s securities. The Company’s officers, employees, and Board members are not entitled to receive grants from the Consultant Plan. The Compensation Committee is authorized to administer the Consultant Plan and establish the grant terms. The Consultant Plan provides for quarterly increases in the available number of authorized shares equal to the lesser of 1% of any new shares issued by the Company during the quarter immediately prior to the adjustment date or such lesser amount as the Board shall determine.

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The Consultant Plan activity is as follows:

	June 30,
(in thousands)	2025
Reserved but unissued shares at beginning of period		264
Increases in the number of authorized shares		21
Grants		(7)
Reserved but unissued shares at end of period		278

The Consultant Plan compensation expense is summarized as follows:

	For the Three Months Ended				For the Six Months Ended
	June 30,				June 30,
(in thousands, except per share data)	2025		2024		2025		2024
Share-based compensation expense	$	3	$	3	$	7	$	6
Weighted average value per share	$	0.94	$	0.81	$	0.94	$	0.81

Note 8 – Net Loss per Common Share

The Company calculates net loss per common share in accordance with ASC Topic 260, “Earnings Per Share” (“ASC 260”). Basic and diluted net loss per common share was determined by dividing net loss applicable to common stockholders by the weighted average number of shares of common stock outstanding during the period. Under ASC 260, shares issuable for little or no cash consideration are considered outstanding common shares and included in the computation of basic net loss per share. As such, for the three and six months ended June 30, 2025 and 2024, the Company included its outstanding pre-funded warrants in its computation of net loss per share. The pre-funded warrants were issued in April and June 2024 and are each exercisable into one share of common stock at an exercise price of $0.0001 per share.

The following potentially dilutive securities have not been included in the computation of diluted net loss per share for the three and six months ended June 30, 2025 and 2024, as the result would be anti-dilutive:

	June 30,	June 30,
(in thousands)	2025	2024
Stock Options	2,888	3,148
Restricted Stock Units	1,077	682
Warrants	21,272	21,319
Total shares excluded from calculation	25,237	25,149

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Note 9 – Commitments and Contingencies

Litigation

From time to time the Company may become involved in various lawsuits and legal proceedings which arise in the ordinary course of business. Litigation is subject to inherent uncertainties and an adverse result in any such matter may harm the Company’s business. As of the date of this report, the Company is not a party to any material pending legal proceedings or claims that the Company believes will have a material adverse effect on the business, financial condition or operating results.

Indemnification Agreements

The Company maintains indemnification agreements with our directors and officers that may require the Company to indemnify these individuals against liabilities that arise by reason of their status or service as directors or officers, except as prohibited by law.

Note 10 – Government Assistance

During 2022, the Company was awarded a research grant from the Department of Energy (“DOE”) for approximately $250 thousand with the completion of such grant occurring in March 2023. The purpose of the grant was to produce a research paper for a flexible fuel ultra-low NOx process burner capable of burning 100% hydrogen fuel. During 2023, the Company was awarded a Phase 2 grant from the DOE to continue developing this ultra-low NOx hydrogen burner. The Phase 2 grant amount totaled approximately $1.6 million over a two-year period. These awards allow the Company to request reimbursements for expenditures such as labor, material, and administrative costs. During the three and six months ended June 30, 2025, the Company recognized $43 thousand and $91 thousand in reimbursements from the DOE, respectively. During the three and six months ended June 30, 2024, the Company recognized $168 thousand and $216 thousand in reimbursements from the DOE, respectively.

Beginning in 2021, the Company received funds relating to the Oklahoma 21^st Century Quality Jobs Act. The estimated duration of the program is up to 10 years and is designed to attract growth industries to Oklahoma. By reporting quarterly salary statistics and meeting agreed upon employment thresholds, the state remits benefit monies to the Company. During three and six months ended June 30, 2025, the Company did not receive any funds from this program. During three and six months ended June 30, 2024, the Company recognized $16 thousand and $47 thousand in government assistance from this program, respectively.

Note 11 – Subsequent Events

The Company has evaluated subsequent events as of the date of this report and has none to report.

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS AND OTHER INFORMATION CONTAINED IN THIS REPORT

This Quarterly Report on Form 10-Q (this “Form 10-Q” or “report”) contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 and the provisions of Section 27A of the Securities Act of 1933, as amended (the “Securities Act”), and Section 21E of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). Forward-looking statements give our current expectations or forecasts of future events. You can identify these statements by the fact that they do not relate strictly to historical or current facts. You can find many (but not all) of these statements by looking for words such as “approximates,” “believes,” “hopes,” “expects,” “anticipates,” “estimates,” “projects,” “intends,” “plans,” “would,” “should,” “could,” “may,” “will” or other similar expressions in this report. In particular, these include statements relating to future actions; prospective products, applications, customers, and technologies; future performance or results of any products; anticipated expenses; and future financial results. These forward-looking statements are subject to certain risks and uncertainties that could cause actual results to

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differ materially from our historical experience and our present expectations or projections. Factors that could cause actual results to differ materially from those discussed in the forward-looking statements include, but are not limited to:

● our limited cash, history of losses, and our expectation that we will continue to experience operating losses and negative cash flows in the near future;

● our ability to successfully develop and implement our technologies and achieve profitability;

● our limited operating history;

● our ability to maintain the listing of our common stock on the Nasdaq Capital Market (“Nasdaq”);

● changes in government regulations that could substantially reduce, or even eliminate, the need for our technology;

● emerging competition and rapidly advancing technology in our industry that may outpace our technology;

● customer demand for the products and services we develop;

● the impact of competitive or alternative products, technologies, and pricing;

● our ability to manufacture any products we design;

● general economic conditions and events and the impact they may have on us and our potential customers;

● the impact of global supply-chain constraints and the threat of, or implementation of, tariffs on imported or exported goods and materials may adversely affect our commercialization efforts and business operations;

● our revenue has been highly concentrated among a small number or customers, and our results of operations could be harmed if we lose a key revenue source and fail to replace it;

● the impact of a cybersecurity incident or other technology disruption;

● our ability to protect our intellectual property;

● our ability to obtain adequate financing in the future;

● our ability to retain and hire personnel with the experience and talent to develop our products and business;

● our success at managing the risks involved in the foregoing items; and

● other factors discussed in this report and in the section titled “Risk Factors” in our most recent Annual Report on Form 10-K.

Forward-looking statements may appear throughout this report, including, without limitation, Item 2 “Management’s Discussion and Analysis of Financial Condition and Results of Operations.” The forward-looking statements are based upon management’s beliefs and assumptions and are made as of the date of this report. We undertake no obligation to publicly update or revise any forward-looking statements included in this report. You should not place undue reliance on these forward-looking statements.

Unless otherwise stated or the context otherwise requires, the terms “ClearSign,” “we,” “us,” “our” and the “Company” refer to ClearSign Technologies Corporation and its subsidiary, ClearSign Asia Limited.

ITEM 2.MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS

The following discussion and analysis of our financial condition and results of operations should be read in conjunction with the unaudited consolidated condensed financial statements and related notes included elsewhere in this Form 10-Q as well as our audited consolidated financial statements and related notes included in our most recent Annual Report on Form 10-K. In addition to historical information, this discussion and analysis here and throughout this Form 10-Q contains forward-looking statements that involve risks, uncertainties, and assumptions. Our actual results may differ materially from those anticipated in these forward-looking statements due to a number of factors, including but not limited to, the risks described in the section titled “Risk Factors” in our Annual Report on Form 10-K for the year ended December 31, 2024.

Overview

We design and develop technologies for the purpose of decarbonization and improving key performance characteristics of combustion systems, including emission and operational performance, energy efficiency and overall

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cost-effectiveness. Our ClearSign Core™ technology has been proven in full scale industrial test furnaces and boilers and first customer installations are currently operating in normal commercial applications. We have generated nominal revenues from operations to date to meet operating expenses.

We have incurred losses since inception totaling $102.8 million and we expect to experience operating losses and negative cash flow for the foreseeable future. We have historically financed our operations primarily through issuances of equity securities. As of June 30, 2025, we have raised approximately $105.3 million in gross proceeds through the sale of our equity securities. We may need to raise additional capital in the future, however, the significant volatility in the capital markets may negatively affect our ability to raise this additional capital.

In order to generate meaningful revenues, our technologies must gain market recognition and acceptance to develop sufficient recurring sales. In addition, management believes that the successful growth and operation of our business is dependent upon our ability to obtain adequate sources of funding through co-development agreements, strategic partnering agreements, or equity or debt financing to support commercialization of our research and development efforts, protect intellectual property, form relationships with strategic partners and provide for working capital and general corporate purposes. There can be no assurance that we will be successful in achieving our long term plans, or that such plans, if consummated, will result in profitable operations or enable us to continue in the long term as a going concern.

Our costs include employee salaries and benefits, compensation paid to consultants, materials and supplies for prototype development and manufacture, costs associated with development activities including materials, sub-contractors, travel and administration, legal and accounting expenses, sales and marketing costs, general and administrative expenses, and other costs associated with an early stage, publicly traded technology company. We currently have 17 full-time employees. Because using third party expertise and resources is more efficient than maintaining full time resources, we also expect to incur ongoing consulting expenses related to technology development and some administrative, sales and legal functions commensurate with our current level of activities.

The amount that we spend for any specific purpose may vary significantly, and could depend on a number of factors including, but not limited to, the pace of progress of our commercialization and development efforts, actual needs with respect to product testing, development and research, market conditions, and changes in or revisions to our sales and marketing strategies.

Research, development, and commercial acceptance of new technologies are, by their nature, unpredictable.  Although we undertake development and commercialization efforts with reasonable diligence, there can be no assurance that the net proceeds from our securities offerings will be sufficient to enable us to develop our technology to the extent needed to create sufficient future sales to sustain operations.  If the net proceeds from these offerings are insufficient for this purpose, we will consider other options to continue our path to commercialization, including, but not limited to, additional financing through follow-on equity offerings, debt financing, co-development agreements, sale or licensing of developed intellectual or other property, or other alternatives.

We cannot assure that our technologies will be accepted, that we will ever earn revenues sufficient to support our operations, or that we will ever be profitable. Furthermore, we have no committed source of financing, and we cannot assure that we will be able to raise money as and when we need it to continue our operations. If we cannot raise funds as and when we need them, we may be required to scale back our development by reducing expenditures for employees, consultants, business development and marketing efforts or to otherwise severely curtail, or even to cease, our operations.

Recent Developments

Special Committee of the Board of Directors

On February 10, 2025, the Company’s board of directors (the “Board”) formed a special committee of all of its then serving independent directors (the “Special Committee”) to review and analyze purported director nominations by

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certain of our stockholders, and non-stockholders, in connection with the Company’s 2025 annual meeting of stockholders (the “2025 Annual Meeting”), and to manage communications and to negotiate and agree settlements with such purported nominating individuals. The Special Committee entered into that certain Cooperation Agreement, dated May 22, 2025, between us and Anthony DiGiandomenico (the “DiGiandomenico Cooperation Agreement”), and that certain Cooperation Agreement, dated May 22, 2025, between us and Richard Clarkson (the “Clarkson Cooperation Agreement,” and together with the DiGiandomenico Cooperation Agreement, the “Cooperation Agreements”), which agreements required, among other things, the appointment of Mr. DiGiandomenico and Louis J. Basenese to the Board. Following the 2025 Annual Meeting, the Special Committee was dissolved.

Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard

On April 1, 2025, we received a letter (the “Notice”) from Nasdaq’s Listing Qualifications Staff (the “Staff”) indicating that, based upon the closing bid price of our common stock for the 30 consecutive business days beginning on February 18, 2025, and ending on March 31, 2025, we no longer meet the requirement to maintain a minimum bid price of $1 per share, as set forth in Nasdaq Listing Rule 5550(a)(2).

In accordance with Nasdaq Listing Rule 5810(c)(3)(A), we have been provided a period of 180 calendar days, or until September 29, 2025, in which to regain compliance. In order to regain compliance with the minimum bid price requirement, the closing bid price of our common stock must be at least $1 per share for a minimum of ten consecutive business days during this 180 day period. In the event that we do not regain compliance within this 180 day period, we may be eligible to seek an additional compliance period of 180 calendar days if it meets the continued listing requirement for market value of publicly held shares and all other initial listing standards for Nasdaq, with the exception of the bid price requirement, and provides written notice to Nasdaq of its intent to cure the deficiency during this second compliance period, by effecting a reverse stock split, if necessary. However, if it appears to the Staff that we will not be able to cure the deficiency, or if we are not otherwise eligible, Nasdaq will provide notice to us that our common stock will be subject to delisting.

The Notice does not result in the immediate delisting of our common stock from Nasdaq. We intend to monitor the closing bid price of our common stock and consider its available options in the event that the closing bid price of our common stock remains below $1 per share.

Stockholder Cooperation Agreements

On May 22, 2025, we entered into the Clarkson Cooperation Agreement with Mr. Clarkson (collectively with his affiliates and associates, the “Clarkson Parties”) and the DiGiandomenico Cooperation Agreement with Mr. DiGiandomenico (collectively with his affiliates and associates, the “DiGiandomenico Parties”).

Pursuant to the Cooperation Agreements, the Clarkson Parties, in connection with the Clarkson Cooperation Agreement, and the DiGiandomenico Parties, in connection with the DiGiandomenico Cooperation Agreement, each, among other things, (a) acknowledged the irrevocable withdrawal of letters they previously delivered to the Company purporting to notify the Company of intent to nominate a director for election to the Board at the 2025 Annual Meeting, and (b) agreed to irrevocably withdraw all outstanding materials and purported notices submitted to the Company, and cease all solicitation efforts and other activities, in connection with or related thereto.

Pursuant to the Cooperation Agreements, the Board increased its size from five to seven directors, appointed Messrs. Basenese and DiGiandomenico (each, a “New Director” and together, the “New Directors”) to the Board, and nominated each New Director as a candidate for election to the Board at the 2025 Annual Meeting.

From the Effective Date until the earlier of (x) the date immediately following the conclusion of the Company’s 2026 annual meeting of stockholders and (y) the occurrence of a Change of Control transaction (as defined in the Cooperation Agreements) (together, such term lengths of the Cooperation Agreements, the “Term”), the Clarkson Parties and the DiGiandomenico Parties have agreed to vote all Voting Securities (as defined in the Cooperation Agreements) beneficially owned by them at all meetings of the Company’s stockholders, or to execute a consent with respect to such

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Voting Securities, in accordance with the Board’s recommendations on all proposals submitted to stockholders, except that the Clarkson Parties and the DiGiandomenico Parties may vote in their discretion on any proposal of the Company in respect of any Extraordinary Transaction (as defined in the Cooperation Agreements). The Clarkson Parties and the DiGiandomenico Parties have also agreed to certain customary standstill provisions during the Term, prohibiting them from, among other things, (i) soliciting proxies, (ii) communicating with stockholders of the Company pursuant to Rule 14a-1(l)(2)(iv) under the Exchange Act, (iii) taking public actions to change or influence the Board, management or the direction of certain Company matters, and (iv) acquiring an aggregate beneficial ownership of more than 3.5% of the outstanding shares of the Company’s common stock or Voting Securities.

During the Term, the Company and the Clarkson Parties and the DiGiandomenico Parties, as applicable, have agreed that they will not disparage each other and that they will not threaten, initiate, encourage or pursue, alone or in concert with others, or knowingly assist any other person to threaten, initiate, encourage or pursue, any lawsuit, claim, or proceeding with respect to any claims against the Company or a Clarkson Party or DiGiandomenico Party, as applicable, except for any legal proceeding initiated solely to remedy a breach of or to enforce the Cooperation Agreements. The Clarkson Parties and the DiGiandomenico Parties have also granted the Company a general release from any claims arising on or prior to the date of the applicable Cooperation Agreement, subject to limited exceptions.

Termination of At The Market Agreement with Virtu

Effective as of July 12, 2025, we terminated its At-the-Market Sales Agreement (the “Virtu ATM Agreement”), dated as of December 23, 2020, that we entered into with Virtu Americas LLC (“Virtu”). Pursuant to the Virtu ATM Agreement, we could offer and sell, from time to time, through or to Virtu, shares of our common stock having an aggregate offering price of up to $8,700,000.

At The Market Agreement with H.C. Wainwright

On July 17, 2025, we entered into an At The Market Offering Agreement (the “ATM Agreement”) with H.C. Wainwright & Co., LLC (“Wainwright”). In accordance with the terms of the ATM Agreement, we may offer and sell from time to time through Wainwright, acting as sales agent, shares of our common stock having an aggregate offering price of up to $10,390,000 (the “Placement Shares”). The Placement Shares will be issued pursuant to the Company’s shelf registration statement on Form S-3 (File No. 333-288736) filed with the Securities and Exchange Commission on July 17, 2025 (the “Registration Statement”) and the prospectus relating to the offer and sale of the Placement Shares that forms a part of the Registration Statement, which was declared effective on July 28, 2025.

Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard

On August 8, 2025, we received a notice (the “Second Notice”) from Nasdaq’s Listing Qualifications Department stating that we are not in compliance with the board of directors independence requirement set forth in Nasdaq Listing Rule 5605(b)(1) and the audit committee composition requirement set forth in Nasdaq Listing Rule 5605(c)(2)(A) (collectively, the “Nasdaq Composition Requirements”) due to the resignations of Catharine M. de Lacy and Judith S. Schrecker from the Board on August 4, 2026.

Specifically, when the Second Notice was issued, the Board did not have a majority of directors that would be considered “independent directors,” as that term is defined in Nasdaq Listing Rule 5605(a)(2), and the Audit and Risk Committee of the Board (the “Audit Committee”) consisted of only two independent directors, rather than the minimum three independent directors as required by Nasdaq Listing Rule 5605(c)(2)(A).

We intend to regain compliance with the Nasdaq Composition Requirements by appointing a new director to the Board and Audit Committee who meets the independence requirements under Nasdaq rules and Rule 10A-3(b)(1) under the Exchange Act. Consistent with Nasdaq Listing Rules 5605(b)(1)(A) and 5605(c)(4), Nasdaq has provided us a cure period in order to regain compliance with the Nasdaq Composition Requirements (i) until the earlier of our next annual

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meeting of stockholders or one year from the resignation of Mss. de Lacy and Schrecker, or August 4, 2026, or (ii) if our next annual meeting of stockholders is held before February 2, 2026, then no later than February 2, 2026.

The Second Notice has no immediate effect on the listing of our common stock on Nasdaq.

Critical Accounting Policies

The following discussion and analysis of financial condition and results of operations is based upon our condensed consolidated financial statements, which have been prepared in conformity with accounting principles generally accepted in the United States. Certain accounting policies and estimates are particularly important to the understanding of our financial position and results of operations. These policies and estimates require the application of significant judgment by management. These estimates can be materially affected by changes from period to period as economic factors and conditions outside of our control change. As a result, they are subject to an inherent degree of uncertainty. In applying these policies, our management uses their judgment to determine the appropriate assumptions to be used in the determination of certain estimates. Those estimates are based on our historical operations, our future business plans and projected financial results, the terms of existing contracts, our observance of trends in the industry, information provided by our customers and information available from other outside sources, as appropriate. We believe the current assumptions and other considerations used to estimate amounts reflected in the condensed consolidated financial statements included in this Form 10-Q are appropriate.

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This Form 10-Q and our most recent Annual Report on Form 10-K include discussions of our accounting policies, as well as methods and estimates used in the preparation of our audited consolidated financial statements. For further information on our critical accounting policies and estimates, see “Item 7 – Management’s Discussion and Analysis of Financial Condition and Results of Operations” in our most recent Annual Report on Form 10-K, the notes to our audited consolidated financial statements included in our most recent Annual Report on Form 10-K and “Note 2 – Summary of Significant Accounting Policies” of our unaudited condensed consolidated financial statements included elsewhere in this Form 10-Q. Since our most recent Annual Report on Form 10-K, we have not experienced a material change to our critical accounting policies or the methods and applications used to develop our accounting estimates.

Results of Operations

Comparison of the Three and Six Months Ended June 30, 2025 and 2024

Highlights of our quarter financial performance are as follows:

	For the Three Months Ended
(in thousands, except per share data)	June 30,
	2025		2024		$ Change		% Change
Revenues	$	133	$	45	$	88	NM
Cost of goods sold		78		3	$	75	NM
Gross profit		55		42	$	13	31.0	%
Research and development		247		402	$	(155)	(38.6)	%
General and administrative		1,646		1,777	$	(131)	(7.4)	%
Operating expenses		1,893		2,179	$	(286)	(13.1)	%
Other income, net		158		265	$	(107)	(40.4)	%
Net loss	$	(1,680)	$	(1,872)	$	192	10.3	%
Basic and diluted net loss per common share	$	(0.03)	$	(0.04)	$	0.01	25.0	%
NM = Not meaningful

	For the Six Months Ended
(in thousands, except per share data)	June 30,
	2025		2024		$ Change		% Change
Revenues	$	534	$	1,147	$	(613)	(53.4)	%
Cost of goods sold		283		668	$	(385)	(57.6)	%
Gross profit		251		479	$	(228)	(47.6)	%
Research and development		694		683	$	11	1.6	%
General and administrative		3,652		3,185	$	467	14.7	%
Operating expenses		4,346		3,868	$	478	12.4	%
Other income, net		339		409	$	(70)	(17.1)	%
Net loss	$	(3,756)	$	(2,980)	$	(776)	(26.0)	%
Basic and diluted net loss per common share	$	(0.07)	$	(0.07)	$	-	-	%

Revenues and Gross Profit

Consolidated revenues for the three months ended June 30, 2025 were $133 thousand compared to $45 thousand for the same period in 2024, and were predominantly generated by delivering spare parts orders to multiple customers and a boiler burner order to a repeat customer. Revenues for the three months ended June 30, 2024 were predominantly related to engineering services provided to customers as part of our contractual performance obligations.

Consolidated revenues for the six months ended June 30, 2025 were $534 thousand compared to $1,147 thousand for the same period in 2024, and were predominantly generated by delivering spare parts orders to multiple customers, delivering a boiler burner to a repeat customer, and successfully completing multiple CFD analyses. Revenues for the six months ended June 30, 2024 were predominantly generated from our process burner line. Specifically, we shipped multiple process burners, executed consulting services, and delivered spare parts related to

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orders from our California refinery customer. For a different customer, an engineering study and CFD analysis was successfully accepted by the customer, which analysis satisfied a contractual performance obligation for this customer.

Gross profit increased by $13 thousand, or 31.0%, and decreased by $228 thousand, or 47.6%, for the three and six months ended June 30, 2025, respectively, as compared to the same time periods in 2024. The favorable increase in gross profit for the three months ended June 30, 2025 was predominantly due to higher revenues during the three months ended June 30, 2025. This increase was partially offset by a $69 thousand decrease in profit margin, which was predominantly due to the lower profit margin of delivering spare parts in the three months ended June 30, 2025, compared to the profit margin of engineering services that we provided in the same period in 2024. During the six months ended June 30, 2025, our unfavorable decrease in gross profit was predominantly due to lower revenues.

Operating Expenses

Operating expenses consist of research and development (“R&D”) and general and administrative (“G&A”) expenses. These are addressed separately below.

Research and Development

R&D expenses decreased $155 thousand, or 38.6%, and increased $11 thousand, or 1.6%, for the three and six months ended June 30, 2025, respectively, as compared to the same time periods in 2024. The favorable decrease in R&D expenses during the three months ended June 30, 2025 was predominantly driven by a year-over-year decrease in product development costs of $168 thousand related to our process burner product line. R&D expenses during the six months ended June 30, 2025 remained relatively consistent year-over-year.

General and Administrative

G&A expenses decreased $131 thousand, or 7.4%, for the three months ended June 30, 2025, as compared to the same time period in 2024. We experienced year-over-year savings of $260 thousand related to the vesting of restricted stock units triggered by the departure of a member of our Board during the three months ended June 30, 2024, which did not occur during the same period in 2025. Our labor and overhead expenses also decreased by $105 thousand during the three months ended June 30, 2025 compared to the same period in 2024, primarily due to certain contract work we performed to one of our U.S. Gulf Coast refinery customers during the three months ended June 30, 2025. These labor and overhead costs were capitalized onto the unaudited condensed consolidated balance sheet within our “Contract Assets” account and will be released to “Cost of Goods Sold” when we recognize revenue for this customer order. Decreases in G&A expenses for the three months ended June 30, 2025 were partially offset by an increase in expenses related to an accrual for legal fees of $300 thousand pertaining to work performed for the Special Committee (see “Recent Developments – Special Committee of the Board of Directors” above for additional information), and an accrual of $22 thousand for the reimbursement of certain legal fees incurred by the Clarkson Parties and DiGiandomenico Parties (each as defined above) in connection with the Cooperation Agreements (as defined above) they entered into with us (see “Recent Developments – Stockholder Cooperation Agreements” above for additional information).

G&A expenses for the six months ended June 30, 2025, increased by $467 thousand, or 14.7%, compared to the same period in 2024. This unfavorable increase in G&A expenses was primarily due to an increase of $903 thousand in legal fees, including (i) $131 thousand in legal fees pertaining to work performed in connection with a regulatory inquiry by the SEC into the trading of our securities in 2020; (ii) an accrual of $750 thousand in legal fees pertaining to work performed for the Special Committee (see “Recent Developments – Special Committee of the Board of Directors” above for additional information); and (iii) an accrual of $22 thousand for the reimbursement of certain legal fees incurred by the Clarkson Parties and DiGiandomenico Parties in connection with the Cooperation Agreements they entered into with us (see “Recent Developments – Stockholder Cooperation Agreements” above for additional information). Increases in G&A expenses for the six months ended June 30, 2025 were partially offset by decreases of $260 thousand related to the vesting of restricted stock units that did not occur compared to the same period in 2024 and $105 thousand for labor and overhead expenses as described in the above paragraph.

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Other Income, Net

Other income, net decreased by $107 thousand, or 40.4%, for the three months ending June 30, 2025, as compared to the same period in 2024. The unfavorable decrease is primarily due to $125 thousand decrease in government assistance from our Department of Energy hydrogen burner development grant. The decrease in grant funding is primarily the result of the timing related to scheduling the burner test facility, which caused a delay in our development activities. The decrease in other income, net for the three months ended June 30, 2025 was partially offset by an increase of $38 thousand in interest income driven by our year-over-year cash position.

Other income, net for the six months ended June 30, 2025 was relatively unchanged compared to the same time period in 2024.

Liquidity and Capital Resources

At June 30, 2025, our cash and cash equivalents balance totaled $12,339 thousand compared to $14,035 thousand at December 31, 2024, a decrease of $1,696 thousand. The decrease in cash and cash equivalent balance is primarily attributable to our net loss of $3,756 thousand which was partially offset by our non-cash expenses of $245 thousand and an increase in contract liabilities of $1,603 thousand.

At June 30, 2025, our current assets were in excess of current liabilities resulting in working capital of $9,480 thousand as compared to $12,809 thousand at December 31, 2024. We believe we have sufficient cash and expected cash collections to fund current operating expenses for over twelve months. We have no contractual debt obligations and to the extent we may require additional funds beyond twelve months from the date hereof, and customer cash collections cannot fund our needs, we may utilize equity offerings. Historically, we have funded operations predominantly through equity offerings. Until the growth of revenue increases to a level that covers our operating expenses, we intend to continue to fund operations in this manner, although the volatility in the capital markets may negatively affect our ability to do so. As of June 30, 2025, approximately 21.3 million shares of our common stock are issuable upon exercise of our outstanding warrants, which number excludes the shares of common stock issuable upon exercise of our outstanding pre-funded warrants, and we may receive up to $22.5 million in aggregate gross proceeds from the cash exercises thereof, subject to certain beneficial ownership limitations set forth therein. These warrants require the warrant holder to tender cash upon exercise, with the exception of the warrants issued to Public Ventures LLC as compensation for their services in connection with our public offering and concurrent private placement in April 2024, which allow the holder to exercise cashless if they so desire. These equity financial instruments may from time-to-time fund future cash needs, but the volatility of our common stock price and the risk tolerance of warrant holders will determine the extent in which we will be able to raise funds in this manner.

Operating activities for the six months ended June 30, 2025, resulted in cash outflows of $1,622 thousand, primarily due to the net loss of $3,756 thousand partially offset by non-cash expenses of $245 thousand and an increase in contract liabilities of $1,603 thousand during such period. The change in contract liabilities during the six months ended June 30, 2025, was impacted by customer collections for orders we have yet to complete

Operating activities for the six months ended June 30, 2024, resulted in cash outflows of $2,525 thousand, primarily due to the net loss for the period of $2,980 thousand, offset with non-cash expense of $519 thousand.

Investing activities for the six months ended June 30, 2025, resulted in cash outflows of $57 thousand, which is primarily attributable to disbursements for patents and other intangible assets.

Investing activities for the six months ended June 30, 2024, resulted in cash outflows of $117 thousand, which is primarily attributable to $99 thousand of disbursements for patents and other intangible assets.

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Financing activities for the six months ended June 30, 2025, resulted in cash outflows of $17 thousand, which is primarily attributable to $41 thousand of disbursements related to taxes paid for the vesting of certain employee restricted stock units, partially offset by $24 thousand in net proceeds received from the exercise of our warrants.

Financing activities for the six months ended June 30, 2024, resulted in cash inflows of $12,936 thousand, which is primarily attributable to the issuance of securities in connection with our public offering and concurrent private placement in April 2024, offset by $31 thousand in disbursements for taxes paid related to vesting of employee restricted stock units.

Off-Balance Sheet Transactions

We do not have any off-balance sheet transactions.

ITEM 3.QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK

As a smaller reporting company, we are not required to provide this information.

ITEM 4.CONTROLS AND PROCEDURES

Disclosure Controls and Procedures

We maintain disclosure controls and procedures, as defined in Rules 13a-15(e) and 15d-15(e) under the Exchange Act, that are designed to reasonably ensure that information required to be disclosed in our reports filed under the Exchange Act, is recorded, processed, summarized and reported within the time periods specified in the Securities and Exchange Commission’s rules and forms, and that such information is accumulated and communicated to our management, including our principal executive officer and principal accounting and financial officer, as appropriate, to allow timely decisions regarding required disclosure.

We carried out an evaluation under the supervision and with the participation of management, including our Chief Executive Officer (principal executive officer) and our Chief Financial Officer (principal accounting and financial officer), of the effectiveness of the design and operation of our disclosure controls and procedures as of June 30, 2025, the end of the period covered by this Form 10-Q. Based upon the evaluation of our disclosure controls and procedures as of June 30, 2025, our Chief Executive Officer (principal executive officer) and our Chief Financial Officer (principal accounting and financial officer) concluded that, as of such date, our disclosure controls and procedures were effective at the reasonable assurance level.

Changes in Internal Control over Financial Reporting

There have been no changes in our internal control over financial reporting that occurred during the quarter ended June 30, 2025 that have materially affected, or are reasonably likely to materially affect, our internal control over financial reporting.

Limitations on Effectiveness of Controls and Procedures

Our management, including our Chief Executive Officer (principal executive officer) and our Chief Financial Officer (principal accounting and financial officer), does not expect that our disclosure controls and procedures or our internal control over financial reporting will prevent or detect all errors and all fraud. A control system, no matter how well conceived and operated, can provide only reasonable, not absolute, assurance that the objectives of the control system are met. Further, the design of a control system must reflect the fact that there are resource constraints, and the benefits of controls must be considered relative to their costs. Because of the inherent limitations in all control systems, no evaluation of controls can provide absolute assurance that all control issues and instances of fraud, if any, have been detected. These inherent limitations include the realities that judgments in decision making can be faulty, and that breakdowns can occur because of a simple error or mistake. Additionally, controls can be circumvented by the individual

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acts of some persons, by collusion of two or more people or by management override of the controls. The design of any system of controls is also based in part upon certain assumptions about the likelihood of future events, and there can be no assurance that any design will succeed in achieving its stated goals under all potential future conditions. Over time, controls may become inadequate because of changes in conditions, or the degree of compliance with policies or procedures. Because of the inherent limitations in a cost-effective control system, misstatements due to error or fraud may occur and not be detected.

PART II - OTHER INFORMATION

ITEM 1.LEGAL PROCEEDINGS

From time to time, we may become involved in various lawsuits and legal proceedings which arise in the ordinary course of business. However, litigation is subject to inherent uncertainties and an adverse result in these or other matters may arise from time to time that may harm our business. We are currently not aware of any such legal proceedings or claims that we believe will have a material adverse effect on our business, financial condition or operating results.

ITEM 1A.RISK FACTORS

We incorporate herein by reference the risk factors included under “Part I - Item 1A. Risk Factors” of our Annual Report on Form 10-K for the year ended December 31, 2024 which we filed with the SEC on March 31, 2025. There are no material changes from the risk factors set forth in such prior filing, except as set forth below.

Our ability to utilize our common stock to finance future capital needs, or for other purposes, is limited by the number of authorized shares of common stock currently available for issuance.

We have authority to issue a total of 87,500,000 shares of common stock, of which 52,426,282 shares of common stock have been issued and approximately 30,000,000 shares of common stock are reserved for issuance in connection with certain securities issued under our equity incentive plans and other outstanding securities, including stock options and warrants.

We have historically financed our operations primarily through issuances of equity securities. With the limited shares of common stock presently available for issuance, our ability to secure additional financing through the sale of common stock, to the extent needed, is limited. Absent an increase in the shares of common stock authorized to be issued under our certificate of incorporation, we will be limited to other financing structures in the event additional financing is required. Such alternative structures may be less favorable or unavailable in which case we may be forced to forego opportunities or required to downsize operations due to lack of funding.

If we fail to comply with Nasdaq’s continued minimum closing bid requirements by September 29, 2025 or other requirements for continued listing, including stockholder equity requirements, our common stock may be delisted and the price of our common stock and our ability to access the capital markets could be negatively impacted.

Our common stock is listed for trading on Nasdaq, therefore, we must satisfy Nasdaq’s continued listing requirements, including, among other things, a minimum closing bid price requirement of $1.00 per share for 30 consecutive business days. On April 1, 2025, the Staff notified us that we did not comply with the minimum bid price requirement for continued listing, as set forth in Nasdaq Listing Rule 5550(a)(2), during the 30 consecutive business day period beginning on February 18, 2025, and ending March 31, 2025. We have been granted 180 calendar days, or until September 29, 2025, to regain compliance. In the event that we do not regain compliance within this 180 period, we may be eligible to seek an additional compliance period of 180 days if we meet certain requirements.

There can be no assurance that we will be able to regain compliance with Nasdaq’s listing rules. If we are unable to regain compliance with the minimum bid price requirement or if we fail to meet any of the other continued listing requirements, including stockholder equity requirements, our securities may be delisted from Nasdaq, which could

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reduce the liquidity of our common stock materially and result in a corresponding material reduction in the price of our common stock. In addition, delisting could harm our ability to raise capital on terms acceptable to us, or at all, and may result in the potential loss of confidence by investors, employees and business development opportunities.

We are subject to risks associated with proxy contests and other actions of activist stockholders.

On February 10, 2025, the Board formed the Special Committee to review and analyze purported director nominations by certain of our stockholders, and non-stockholders, in connection with our 2025 Annual Meeting, and to manage communications and to negotiate and agree settlements with such purported nominating individuals. On May 22, 2025, the Special Committee entered into the Cooperation Agreements, which agreements required, among other things, the appointment of Messrs. DiGiandomenico and Basenese to the Board. Following the 2025 Annual Meeting, the Special Committee was dissolved.

Any legal challenges or other actions by stockholders could result in costly and time-consuming litigation, interfere with our ability to execute our business plan, give rise to perceived uncertainties as to our future direction, adversely affect our relationships with customers, suppliers, investors, prospective and current team members and others, result in the loss of potential business opportunities, or make it more difficult to attract and retain qualified personnel, any of which could materially and adversely affect our business and operating results. The market price of our common stock could be subject to significant fluctuation or otherwise be adversely affected by the events, risks and uncertainties related to any such stockholder activism.

ITEM 2.UNREGISTERED SALES OF EQUITY SECURITIES AND USE OF PROCEEDS

On November 13, 2024, the Board authorized issuance of 15,000 shares to be remitted in quarterly installments to our investor relations firm, Firm IR Group LLC (“Firm IR”), for services rendered by them, pursuant to our 2013 Consultant Stock Plan. On June 30, 2025, we issued 3,750 shares of common stock to Firm IR at a fair market value price per share of $0.94, the closing price of our common stock as reported on Nasdaq on November 13, 2024, the date of grant. These shares were issued in reliance upon the exemption from registration provided by Section 4(a)(2) of the Securities Act, for a transaction by an issuer not involving a public offering.

ITEM 3.DEFAULTS UPON SENIOR SECURITIES

Not applicable.

ITEM 4.MINE SAFETY DISCLOSURES

Not applicable.

ITEM 5.OTHER INFORMATION

None of the Company’s directors or officers adopted, modified or terminated a Rule 10b-5 trading arrangement or a non-Rule 10b-5 trading arrangement during the fiscal quarter ended June 30, 2025, as such terms are defined under Item 408(a) of Regulation S-K.

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Item 6. Exhibit	EXHIBITS
Number		Document
3.1		Certificate of Incorporation of ClearSign Technologies Corporation, a Delaware corporation (incorporated by reference to Exhibit 3.3 of the Company’s Form 8-K filed with the Securities and Exchange Commission on June 15, 2023).
3.2		Certificate of Amendment, as filed with the Secretary of the State of Delaware on June 25, 2024 (incorporated by reference to Exhibit 3.1 of the Company’s Form 8-K filed with the Securities and Exchange Commission on June 26, 2024).
3.3		Bylaws of ClearSign Technologies Corporation, a Delaware corporation (incorporated by reference to Exhibit 3.4 of the Company’s Form 8-K filed with the Securities and Exchange Commission on June 15, 2023).
4.1		Form of Common Warrant (incorporated by reference to Exhibit 4.1 of the Company’s Form 8-K filed with the Securities and Exchange Commission on April 19, 2024).
4.2		Form of Underwriter’s Warrant (incorporated by reference to Exhibit 4.2 of the Company’s Form 8-K filed with the Securities and Exchange Commission on April 19, 2024).
4.3		Form of Private Warrant (incorporated by reference to Exhibit 4.3 of the Company’s Form 8-K filed with the Securities and Exchange Commission on April 19, 2024).
4.4		Form of Pre-Funded Warrant (incorporated by reference to Exhibit 4.1 of the Company’s Form 8-K filed with the Securities and Exchange Commission on April 23, 2024).
4.5		Form of Placement Agent Warrant (incorporated by reference to Exhibit 4.4 of the Company’s Form 8-K filed with the Securities and Exchange Commission on April 19, 2024).
10.1		Cooperation Agreement, dated May 22, 2025, by and between ClearSign Technologies Corporation and Richard D. Clarkson (incorporated by reference to Exhibit 10.1 of the Company’s Form 8-K filed with the Securities and Exchange Commission on May 27, 2025).
10.2		Cooperation Agreement, dated May 22, 2025, by and between ClearSign Technologies Corporation and Anthony DiGiandomenico (incorporated by reference to Exhibit 10.2 of the Company’s Form 8-K filed with the Securities and Exchange Commission on May 27, 2025).
10.3+		Louis J. Basenese’s Offer Letter, effective as of May 22, 2025 (incorporated by reference to Exhibit 10.3 of the Company’s Form 8-K filed with the Securities and Exchange Commission on May 27, 2025).
10.4+		Anthony DiGiandomenico’s Offer Letter, effective as of May 22, 2025 (incorporated by reference to Exhibit 10.4 of the Company’s Form 8-K filed with the Securities and Exchange Commission on May 27, 2025).
31.1*		Rule 13a-14(a)/15d-14(a) Certification of Principal Executive Officer.
31.2*		Rule 13a-14(a)/15d-14(a) Certification of Principal Financial Officer.

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32.1**	Section 1350 Certification of Principal Executive Officer and Principal Financial Officer.
101.INS*	Inline XBRL Instance Document.
101.SCH*	Inline XBRL Taxonomy Extension Schema Document.
101.CAL*	Inline XBRL Taxonomy Extension Calculation Linkbase Document.
101.DEF*	Inline XBRL Taxonomy Extension Definition Linkbase Document.
101.LAB*	Inline XBRL Taxonomy Extension Label Linkbase Document.
101.PRE*	Inline XBRL Taxonomy Extension Presentation Linkbase Document.
104*	Cover Page Interactive Data File (formatted as inline XBRL and contained in Exhibit 101).

*Filed herewith.

**Furnished herewith.

+ Agreement with management or compensatory plan or arrangement.

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

		CLEARSIGN TECHNOLOGIES CORPORATION
Date: August 14, 2025	By:	/s/ Colin James Deller
		Colin James Deller
		Chief Executive Officer
		(Principal Executive Officer)

Date: August 14, 2025	By:	/s/ Brent Hinds
		Brent Hinds
		Chief Financial Officer (Principal Financial and Accounting Officer)

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EX-31.1

Exhibit 31.1

CERTIFICATION

I, Colin James Deller, certify that:

1. I have reviewed this quarterly report on Form 10-Q of ClearSign Technologies Corporation;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15-d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including any consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c) Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d) Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting;

5. The registrant’s other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date: August 14, 2025

/s/ Colin James Deller

Colin James Deller

Chief Executive Officer

(Principal Executive Officer)

EX-31.2

Exhibit 31.2

CERTIFICATION

I, Brent Hinds, certify that:

1. I have reviewed this quarterly report on Form 10-Q of ClearSign Technologies Corporation;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15-d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including any consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c) Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d) Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting;

5. The registrant’s other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date: August 14, 2025

/s/ Brent Hinds

Brent Hinds

Chief Financial Officer

(Principal Financial and Accounting Officer)

EX-32.1

Exhibit 32.1

CERTIFICATION

In connection with the quarterly report on Form 10-Q of ClearSign Technologies Corporation (the “Company”) for the period ended June 30, 2025 as filed with the Securities and Exchange Commission (the “Report”), we, Colin James Deller, Chief Executive Officer (Principal Executive Officer) and Brent Hinds, Chief Financial Officer (Principal Financial and Accounting Officer) of the Company, hereby certify as of the date hereof, solely for purposes of Rule 13a-14(b) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”) and Title 18, Chapter 63, Section 1350 of the United States Code, that to the best of my knowledge:

(1) The Report fully complies with the requirements of Section 13(a) or 15(d), as applicable, of the Exchange Act, and

(2) The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company at the dates and for the periods indicated.

Date: August 14, 2025

/s/ Colin James Deller

Colin James Deller

Chief Executive Officer

(Principal Executive Officer)

/s/ Brent Hinds

Brent Hinds

Chief Financial Officer

(Principal Financial and Accounting Officer)

This certification accompanies the Form 10-Q to which it relates, is not deemed filed with the Securities and Exchange Commission and is not to be incorporated by reference into any filing of the Company under the Securities Act of 1933, as amended, or the Exchange Act (whether made before or after the date of the Report), irrespective of any general incorporation language contained in such filing.

XML

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2025	Aug. 06, 2025
Document and Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2025
Document Transition Report	false
Entity File Number	001-35521
Entity Registrant Name	CLEARSIGN TECHNOLOGIES CORPORATION
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-2056298
Entity Address, Address Line One	8023 E. 63rd Place, Suite 101
Entity Address, City or Town	Tulsa
Entity Address, State or Province	OK
Entity Address, Postal Zip Code	74133
City Area Code	918
Local Phone Number	236-6461
Title of 12(b) Security	Common Stock
Trading Symbol	CLIR
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		52,426,282
Entity Central Index Key	0001434524
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2025
Document Fiscal Period Focus	Q2
Amendment Flag	false

XML

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Current Assets:
Cash and cash equivalents	$ 12,339	$ 14,035
Accounts receivable	25	165
Contract assets	268	194
Prepaid expenses and other assets	550	454
Total current assets	13,182	14,848
Fixed assets, net	251	238
Patents and other intangible assets, net	798	830
Total Assets	14,231	15,916
Current Liabilities:
Accounts payable and accrued liabilities	1,556	1,220
Current portion of lease liabilities	93	75
Accrued compensation and related taxes	378	671
Contract liabilities	1,675	73
Total current liabilities	3,702	2,039
Long Term Liabilities:
Long term lease liabilities	115	113
Total liabilities	3,817	2,152
Commitments and contingencies (Note 9)
Stockholders' Equity:
Preferred stock, $0.0001 par value, 2,000,000 shares authorized, no shares issued or outstanding
Common stock, $0.0001 par value, 87,500,000 shares authorized, 52,426,282 and 50,285,509 shares issued and outstanding at June 30, 2025 and December 31, 2024, respectively	5	5
Additional paid-in capital	113,202	112,796
Accumulated other comprehensive loss	(21)	(21)
Accumulated deficit	(102,772)	(99,016)
Total stockholders' equity	10,414	13,764
Total Liabilities and Stockholders' Equity	$ 14,231	$ 15,916

XML

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2025	Dec. 31, 2024
Condensed Consolidated Balance Sheets
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, authorized shares	2,000,000	2,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common Stock, Shares Authorized	87,500,000	87,500,000
Common stock, shares issued	52,426,282	50,285,509
Common stock, shares outstanding	52,426,282	50,285,509

XML

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Condensed Consolidated Statements of Operations and Comprehensive Loss
Revenues	$ 133	$ 45	$ 534	$ 1,147
Cost of goods sold	78	3	283	668
Gross profit	55	42	251	479
Operating expenses:
Research and development	247	402	694	683
General and administrative	1,646	1,777	3,652	3,185
Total operating expenses	1,893	2,179	4,346	3,868
Loss from operations	(1,838)	(2,137)	(4,095)	(3,389)
Other income, net:
Interest income	115	77	248	138
Government assistance	43	185	91	264
Other income, net		3		7
Total other income, net	158	265	339	409
Net loss	$ (1,680)	$ (1,872)	$ (3,756)	$ (2,980)
Net loss per share - basic (in dollar per share)	$ (0.03)	$ (0.04)	$ (0.07)	$ (0.07)
Net loss per share - fully diluted (in dollar per share)	$ (0.03)	$ (0.04)	$ (0.07)	$ (0.07)
Weighted average number of shares outstanding - basic (in shares)	55,217,968	47,312,810	55,107,588	43,080,454
Weighted average number of shares outstanding - fully diluted (in shares)	55,217,968	47,312,810	55,107,588	43,080,454
Comprehensive loss:
Net loss	$ (1,680)	$ (1,872)	$ (3,756)	$ (2,980)
Foreign-exchange translation adjustments		(1)		(4)
Comprehensive loss	$ (1,680)	$ (1,873)	$ (3,756)	$ (2,984)

XML

Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Common Stock Public offering	Common Stock Private Placement	Common Stock Participation Right	Common Stock	Additional Paid-in Capital Public offering	Additional Paid-in Capital Private Placement Warrants	Additional Paid-in Capital Private Placement Prefunded Warrants	Additional Paid-in Capital Private Placement	Additional Paid-in Capital Participation Right Warrants	Additional Paid-in Capital Participation Right Prefunded Warrants	Additional Paid-in Capital Participation Right	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit	Public offering	Private Placement Warrants	Private Placement Prefunded Warrants	Private Placement	Participation Right Warrants	Participation Right Prefunded Warrants	Participation Right	Total
Beginning Balance at Dec. 31, 2023				$ 4								$ 98,922	$ (17)	$ (93,717)								$ 5,192
Beginning Balances (in shares) at Dec. 31, 2023				38,687
Share-based compensation												67										67
Share-based compensation (in shares)				67
Fair value of stock issued in payment of accrued compensation												326										326
Fair value of stock issued in payment of accrued compensation (in shares)				307
Shares issued for services												3										3
Shares issued for services (per share) (in shares)				4
Foreign-exchange translation adjustment													(3)									(3)
Tax withholdings related to share-based compensation												(16)										(16)
Tax withholdings related to share-based compensation (in shares)				(22)
Net loss														(1,108)								(1,108)
Ending Balance at Mar. 31, 2024				$ 4								99,302	(20)	(94,825)								4,461
Ending Balances (in shares) at Mar. 31, 2024				39,043
Beginning Balance at Dec. 31, 2023				$ 4								98,922	(17)	(93,717)								5,192
Beginning Balances (in shares) at Dec. 31, 2023				38,687
Fair value of stock issued in payment of accrued compensation																						$ 326
Fair value of stock issued in payment of accrued compensation (in shares)																						307
Net loss																						$ (2,980)
Ending Balance at Jun. 30, 2024				$ 5								112,602	(21)	(96,697)								15,889
Ending Balances (in shares) at Jun. 30, 2024				50,206
Beginning Balance at Mar. 31, 2024				$ 4								99,302	(20)	(94,825)								4,461
Beginning Balances (in shares) at Mar. 31, 2024				39,043
Share-based compensation												344										344
Share-based compensation (in shares)				256
Shares issued for services												3										3
Shares issued for services (per share) (in shares)				4
Issuance of common stock in offering, net of expenses	$ 1				$ 2,390			$ 865			$ 1,447				$ 2,391			$ 865			$ 1,447
Issuance of common stock in offering, net of expenses (in shares)	5,314	2,250	3,350
Issuance of warrants in offering, net of expenses						$ 2,389	$ 1,214		$ 2,250	$ 580		1,831				$ 2,389	$ 1,214		$ 2,250	$ 580		1,831
Foreign-exchange translation adjustment													(1)									(1)
Tax withholdings related to share-based compensation												(13)										(13)
Tax withholdings related to share-based compensation (in shares)				(11)
Net loss														(1,872)								(1,872)
Ending Balance at Jun. 30, 2024				$ 5								112,602	(21)	(96,697)								15,889
Ending Balances (in shares) at Jun. 30, 2024				50,206
Beginning Balance at Dec. 31, 2024				$ 5								112,796	(21)	(99,016)								13,764
Beginning Balances (in shares) at Dec. 31, 2024				50,286
Share-based compensation, net of tax withholdings												45										45
Share-based compensation, net of tax withholdings (in shares)				81
Fair value of stock issued in payment of accrued compensation												279										279
Fair value of stock issued in payment of accrued compensation (in shares)				326
Shares issued for services												4										4
Shares issued for services (per share) (in shares)				4
Exercise of warrants												24										24
Exercise of warrants (in shares)				23
Exercise of prefunded warrants (in shares)				1,703
Net loss														(2,076)								(2,076)
Ending Balance at Mar. 31, 2025				$ 5								113,148	(21)	(101,092)								12,040
Ending Balances (in shares) at Mar. 31, 2025				52,423
Beginning Balance at Dec. 31, 2024				$ 5								112,796	(21)	(99,016)								13,764
Beginning Balances (in shares) at Dec. 31, 2024				50,286
Fair value of stock issued in payment of accrued compensation																						$ 279
Fair value of stock issued in payment of accrued compensation (in shares)																						326
Net loss																						$ (3,756)
Ending Balance at Jun. 30, 2025				$ 5								113,202	(21)	(102,772)								10,414
Ending Balances (in shares) at Jun. 30, 2025				52,426
Beginning Balance at Mar. 31, 2025				$ 5								113,148	(21)	(101,092)								12,040
Beginning Balances (in shares) at Mar. 31, 2025				52,423
Share-based compensation, net of tax withholdings												51										51
Shares issued for services												3										3
Shares issued for services (per share) (in shares)				3
Net loss														(1,680)								(1,680)
Ending Balance at Jun. 30, 2025				$ 5								$ 113,202	$ (21)	$ (102,772)								$ 10,414
Ending Balances (in shares) at Jun. 30, 2025				52,426

XML

Condensed Consolidated Statement of Stockholders' Equity (Unaudited) (Parenthetical) - $ / shares	3 Months Ended
	Jun. 30, 2024	Mar. 31, 2024
Condensed Consolidated Statements of Stockholders' Equity
Share price of common stock issued for services, two (in dollars per share)	$ 0.81	$ 0.81

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Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024
Cash flows from operating activities:
Net loss	$ (3,756)	$ (2,980)
Adjustments to reconcile net loss to net cash used in operating activities:
Common stock issued for services	7	6
Share-based compensation, net of tax withholdings	96	382
Depreciation and amortization	98	91
Right-of-use asset amortization	44	43
Lease amendments		(3)
Change in operating assets and liabilities:
Contract assets	(75)	183
Accounts receivable	140	152
Prepaid expenses and other assets	(96)	(238)
Accounts payable, accrued liabilities, and lease liabilities	330	78
Accrued compensation and related taxes	(13)	52
Contract liabilities	1,603	(291)
Net cash used in operating activities	(1,622)	(2,525)
Cash flows from investing activities:
Acquisition of fixed assets	(4)	(18)
Disbursements for patents and other intangible assets	(53)	(99)
Net cash used in investing activities	(57)	(117)
Cash flows from financing activities:
Proceeds from issuance of common stock, net of offering costs		12,967
Proceeds from exercise of warrants	24
Taxes paid related to vesting of restricted stock units	(41)	(31)
Net cash provided by (used in) financing activities	(17)	12,936
Effect of exchange rate changes on cash and cash equivalents		(4)
Net change in cash and cash equivalents	(1,696)	10,290
Cash and cash equivalents, beginning of period	14,035	5,684
Cash and cash equivalents, end of period	12,339	15,974
Supplemental disclosure of cash flow information:
Officer and employee equity awards for prior year accrued compensation	279	326
Non-cash impact of new lease	$ 68	$ 32

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Organization and Description of Business

6 Months Ended

Jun. 30, 2025

Organization and Description of Business

Organization and Description of Business

Note 1 – Organization and Description of Business

ClearSign Technologies Corporation (“ClearSign” or the “Company”) designs and develops products and technologies for the purpose of decarbonization and improving key performance characteristics of industrial and commercial systems, including operational performance, energy efficiency, emission reduction, safety, and overall cost-effectiveness. The Company’s patented technologies are designed to be embedded in established original equipment manufacturers (“OEM”) products as ClearSign Core™ and ClearSign Eye and other sensing configurations in order to enhance the performance of combustion systems and fuel safety systems in a broad range of markets. These markets include energy (upstream oil production and down-stream refining), commercial/industrial boiler, chemical, petrochemical, transport and power industries. The Company’s primary technology is its ClearSign Core™ technology, which achieves very low emissions without the need of selective catalytic reduction.

The Company was originally incorporated in the State of Washington in 2008. During January 2022, the Company relocated its headquarters from Seattle, Washington to Tulsa, Oklahoma. Effective June 15, 2023, the Company changed its state of incorporation to Delaware. On July 28, 2017, the Company incorporated a subsidiary, ClearSign Asia Limited, in Hong Kong to represent the Company’s business and technological interests throughout Asia. Through ClearSign Asia Limited, the Company has established a wholly foreign owned enterprise in China – ClearSign Combustion (Beijing) Environmental Technologies Co., LTD. On August 22, 2024, the Company’s Board of Directors (the “Board”) authorized management to move forward with filing for dormancy with Chinese regulators to suspend the Company’s Beijing, China operations. A dormancy filing allows the Company to keep its China legal entity in a suspended status for up to three years. The Company can revive its China operations at any time during those three years with minimal cost impact. The effective date of our dormancy filing was March 12, 2025.

Unless otherwise stated or the context otherwise requires, the terms “we,” “us,” “our,” “ClearSign” and the “Company” refer to ClearSign Technologies Corporation and its subsidiary, ClearSign Asia Limited.

Business Segments

The Company operates in one operating and reportable segment engaged in the design, development and sale of combustion technologies that improve the performance and cost-effectiveness of industrial combustion systems, referred to herein as the “Combustion” segment. The Company manages its business activities on a consolidated basis. Since the operations comprise a single reportable segment, amounts reported in the consolidated balance sheets, statements of operations and comprehensive loss, stockholders’ equity, and cash flows represent the activities of the Combustion segment.

The Combustion segment derives revenues by delivering products and technology solutions to OEM’s and end-users. Our products and solutions can be incorporated into a new or existing customer infrastructure or equipment. Customer contracts can include multiple billing milestones and performance obligations. The Company can typically satisfy its performance obligations within a twelve month period, but customer project delays, some of which can be beyond the Company’s control, can impact timing of performance and there is no assurance we will satisfy all performance obligations in such period of time.

The Company’s Chief Executive Officer, who is the chief operating decision maker (“CODM”), reviews quarterly financial information on a consolidated basis for making operating decisions, allocating resources and evaluating financial performance. The CODM consistently reviews the consolidated statements of operations and comprehensive loss to manage operations and monitor performance against management expectations. Factors considered by the CODM when assessing a reportable segment include factors such as, but not limited to, human capital, intellectual property, customer relationships and business model design.

Substantially all the Company’s operating activities, including its long-lived assets, are located within the United States. Customers in the United States accounted for 100% of revenues during the three and six months ended June 30, 2025 and 2024. The Company disaggregates geographical revenues by selling location, since many of our target customers are global entities, and it would be more likely than not, that these customers would negotiate sales within our current territory in the United States.

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Summary of Significant Accounting Policies

6 Months Ended

Jun. 30, 2025

Summary of Significant Accounting Policies

Summary of Significant Accounting Policies

Note 2 – Summary of Significant Accounting Policies

Basis of Presentation

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the “SEC”) for reporting on Form 10-Q. Accordingly, certain information and footnote disclosures normally included in financial statements prepared in accordance with generally accepted accounting principles have been condensed or omitted pursuant to such rules and regulations. The condensed consolidated balance sheet at December 31, 2024 has been derived from the Company’s audited consolidated financial statements as of that date.

In the opinion of management, these condensed consolidated financial statements reflect all normal recurring and other adjustments necessary for a fair presentation. These condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2024. Operating results for interim periods are not necessarily indicative of operating results for an entire fiscal year or any other future periods.

The accompanying unaudited condensed consolidated financial statements include the accounts of ClearSign and its subsidiary. Intercompany balances and transactions have been eliminated in consolidation.

Use of Estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make certain estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Research and Development

The cost of research and development is expensed as incurred. Research and development costs consist of salaries, benefits, share-based compensation, consumables, and consulting fees, including costs to develop and test prototype equipment and parts. Research and development costs have been offset by funds received, if any, from strategic partners in cost sharing, collaborative projects. During the three and six months ended June 30, 2025, the Company received no funds from these types of arrangements. During the three and six months ended June 30, 2024, the Company received zero and $107 thousand, respectively, from these types of arrangements.

Foreign Operations

The accompanying unaudited condensed consolidated balance sheets as of June 30, 2025 and December 31, 2024 include assets amounting to approximately $170 thousand and $145 thousand, respectively, relating to the operations of ClearSign Asia Limited. The Beijing registered capital requirement is $350 thousand, which is required to be paid by June 30, 2032, and of which $211 thousand has been paid as of June 30, 2025. On August 22, 2024, the Board authorized management to move forward with filing for dormancy with Chinese regulators to suspend the Company’s Beijing, China operations. A dormancy filing allows the Company to keep its China legal entity in a suspended status for up to three years. The Company can revive its China operations at any time during those three years with minimal cost impact. The dormancy filing became effective as of March 12, 2025.

Recently Issued Accounting Pronouncements

In December 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures (“ASU 2023-09”) to enhance the transparency and decision-making usefulness of income tax disclosures by requiring additional information on an entity's tax rate reconciliation, as well as income taxes paid. ASU 2023-09 is effective for our reporting period beginning January 1, 2025. We are currently assessing the impact that the adoption of ASU 2023-09 will have on the disclosures in our annual consolidated financial statements.

In November 2024, FASB issued ASU No. 2024-03, Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40) (“ASU 2024-03”). ASU 2024-03 requires enhanced disclosures about types of expenses, including purchases of inventory, employee compensation, depreciation, and amortization, in commonly presented expense captions. The amendments are effective for fiscal years beginning after December 15, 2026, and interim periods beginning after December 15, 2027, with early adoption permitted. Entities may apply the amendments prospectively or retrospectively to any or all prior periods presented in the financial statements. We are currently evaluating the impact that this guidance will have on the disclosures within our consolidated financial statements. While ASU 2024-03 will impact only our disclosures and not our financial condition and results of operations, we are assessing when we will adopt the ASU 2024-03.

In May 2025, FASB issued ASU No. 2025-04, Compensation—Stock Compensation (Topic 718) and Revenue from Contracts with Customers (Topic 606): Clarifications to Share-Based Consideration Payable to a Customer (“ASU 2025-04”), which clarifies the guidance on the accounting for share-based payment awards that are granted by an entity as consideration payable to its customer, with the intent to reduce diversity in practice and improve existing guidance by revising the definition of a “performance condition” and eliminating a forfeiture policy election for service conditions associated with share-based consideration payable to a customer. ASU 2025-04 also clarifies the guidance in Topic 606 on the variable consideration constraint does not apply to share-based consideration payable to a customer “regardless of whether an award’s grant date has occurred.” ASU 2025-04 is effective for our reporting period beginning January 1, 2027, with early adoption permitted.  We are currently assessing the impact that the adoption of ASU 2025-04 will have on the disclosures in our annual consolidated financial statements.

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Fixed Assets, Net

6 Months Ended

Jun. 30, 2025

Fixed Assets, Net

Fixed Assets, Net

Note 3 – Fixed Assets, Net

Fixed Assets, Net

Fixed assets, net are summarized as follows:

	June 30,		December 31,
(in thousands)	2025		2024
Office furniture and equipment	$	103	$	99
Leasehold improvements		43		43
		146		142
Accumulated depreciation and amortization		(97)		(85)
		49		57
Operating lease ROU assets, net		202		181
Total	$	251	$	238

Depreciation expense for the three and six months ended June 30, 2025 was $7 thousand and $12 thousand, respectively.

Depreciation expense for the three and six months ended June 30, 2024 was $4 thousand and $11 thousand, respectively.

Leases

The Company leases office space in Tulsa, Oklahoma, Seattle, Washington, and Beijing, China. During May 2025, the Company renewed its Beijing, China lease for 24 months with monthly rent at approximately $3 thousand. As a result of this renewal, the Company increased the right-of-use (“ROU”) asset and lease liability by $68 thousand during the six months ended June 30, 2025.

During October 2024, the Company entered into a sub-lease agreement to rent office space in Seattle for approximately $2 thousand per month for twelve months. The Seattle lease is considered a short-term lease, as the lease term is 12 months or less from the commencement date. The short-term lease expense for the three and six months ended June 30, 2025 was approximately $5 thousand and $11 thousand, respectively. The short-term lease expense for the three and six months ended June 30, 2024 was approximately $5 thousand and $11 thousand, respectively. The Tulsa and Beijing leases are classified as operating leases, with remaining terms ranging from two years to approximately three years; contractual language requires renewal negotiations to occur at or near termination. These leases are normal and customary for office space, in that, contractual guarantees exist requiring the lessee return the premises to its original functional state.

The Tulsa lease contains fixed annual lease payments that increase annually by 2%. The Seattle, Tulsa, and Beijing total monthly minimum rent is approximately $10 thousand, in the aggregate. Operating lease costs for the three and six months ended June 30, 2025 was $25 thousand and $49 thousand, respectively. Operating lease costs for the three and six months ended June 30, 2024 was $24 thousand and $48 thousand, respectively.

Supplemental balance sheet information related to operating leases is as follows:

		June 30,			December 31,
(in thousands)		2025			2024
Operating lease ROU assets, net	$	202		$	181
Lease Liabilities:
Current lease liabilities	$	93		$	75
Long term lease liabilities		115			113
Total lease liabilities	$	208		$	188
Weighted average remaining lease term (in years):		2.2			2.6
Weighted average discount rate:		4.4	%		5.3	%

Supplemental cash flow information related to operating leases is as follows:

	For the Six Months Ended
	June 30,
(in thousands)		2025		2024
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows used in operating leases	$	49	$	49
Non-cash impact of new leases and lease modifications
Change in operating lease liabilities	$	68	$	29
Change in operating lease ROU assets	$	68	$	32

Minimum future payments under the Company’s operating lease liabilities as of June 30, 2025 are as follows:

(in thousands)
2025 (remaining)	$	50
2026		101
2027		68
Total future lease payments		219
Less: imputed interest		(11)
	$	208

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Patents and Other Intangible Assets

6 Months Ended

Jun. 30, 2025

Patents and Other Intangible Assets

Patents and Other Intangible Assets

Note 4 – Patents and Other Intangible Assets

Patents and other intangible assets are summarized as follows:

	June 30,		December 31,
(in thousands)	2025		2024
Patents
Patents pending	$	377	$	346
Issued patents		1,056		1,034
		1,433		1,380
Trademarks
Registered trademarks		86		86
		86		86
Other		8		8
		1,527		1,474
Accumulated amortization		(729)		(644)
	$	798	$	830

Amortization expense for three and six months ended June 30, 2025 was $43 thousand and $85 thousand, respectively.

Amortization expense for three and six months ended June 30, 2024 was $42 thousand and $80 thousand, respectively.

Future amortization expense associated with issued patents and registered trademarks as of June 30, 2025 is as follows:

(in thousands)
2025 (remaining)	$	75
2026		130
2027		106
2028		70
2029		30
Thereafter		2
	$	413

The amortization life for patents ranges between three to five years and trademark lives are set at ten years. The Company does not amortize patents or trademarks classified as pending.

During the three and six months ended June 30, 2025 and 2024, the Company assessed its patent and trademark assets. The Company also evaluated its strategic approach to the pursuit and protection of its intellectual property. It is the

intent of the Company to continue to pursue intellectual property protection. If the Company identifies certain assets where the intellectual property does not directly align with its core technology, the Company will impair the intangible asset and write-off the asset as an expense.

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Revenue, Contract Assets and Contract Liabilities

6 Months Ended

Jun. 30, 2025

Revenue, Contract Assets and Contract Liabilities

Revenue, Contract Assets and Contract Liabilities

Note 5 – Revenue, Contract Assets and Contract Liabilities

The Company’s contracts with customers generally have performance obligations and a schedule of non-refundable cancellation obligations. Performance obligations typically fall into one of three categories, product shipment, burner performance tests and engineering design. Customer payment milestones are unique to individual contracts and may occur prior to completion of performance obligations. Customer payment terms typically range between thirty and sixty days from the date of billing. Our customer contracts typically have a duration of less than twelve months. Delays in contract performance, if any, typically occur as a result of customer onsite project delays outside of our control.

The Company recognized $133 thousand of revenues and $78 thousand of cost of goods sold during the three months ended June 30, 2025. The revenue and cost of goods sold relate to spare parts orders from multiple customers, and delivery of a boiler burner to a repeat customer. These products and services constitute performance obligations.

The Company recognized $534 thousand of revenues and $283 thousand of cost of goods sold during the six months ended June 30, 2025. The revenue and cost of goods sold predominantly relate to spare parts orders for multiple customers, sales of boiler burners to a single customer, and the successful completion of an engineering study referred herein as a Computational Fluid Dynamic analysis (“CFD”). These products and services constitute performance obligations.

The Company recognized $45 thousand of revenues and $3 thousand of cost of goods sold during the three months ended June 30, 2024. The revenue and cost of goods sold relate to the successful completion of engineering studies for a repeat customer. These products and services constitute performance obligations.

The Company recognized $1,147 thousand of revenues and $668 thousand of cost of goods sold during the six months ended June 30, 2024. The revenue and cost of goods sold relate predominantly to the Company’s process burner product line. The Company delivered multiple burners in connection with a single customer order, successfully completed engineering studies and a CFD analysis, and fulfilled multiple spare parts orders. These products and services constitute performance obligations.

The Company had contract assets of $268 thousand and $194 thousand at June 30, 2025 and December 31, 2024, respectively. The Company had contract liabilities of $1,675 thousand and $73 thousand at June 30, 2025 and December 31, 2024, respectively. Of the $73 thousand contract liabilities balance at December 31, 2024, the Company recognized revenue of $10 thousand and $33 thousand during the three and six months ended June 30, 2025, respectively.

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Product Warranties

6 Months Ended

Jun. 30, 2025

Product Warranties

Product Warranties

Note 6 – Product Warranties

A summary of the Company’s warranty liability activity, which is included in accounts payable and accrued liabilities in the accompanying condensed consolidated balance sheets as of June 30, 2025 and December 31, 2024, is as follows:

	June 30,		December 31,
(in thousands)	2025		2024
Warranty liability at beginning of year	$	471	$	110
Accruals		46		478
Payments		(162)		(114)
Changes related to expirations and settlements		(24)		(3)
Warranty liability at end of period	$	331	$	471

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Equity

6 Months Ended

Jun. 30, 2025

Equity

Equity

Note 7 – Equity

Common Stock and Preferred Stock

The Company is authorized to issue 87.5 million shares of common stock and 2.0 million shares of preferred stock. Preferences, limitations, voting powers and relative rights of any preferred stock to be issued may be determined by the Board. The Company has not issued any shares of preferred stock.

The Company has an At-The-Market (“ATM”) program pursuant to an ATM Offering Agreement with H.C. Wainwright & Co., LLC (“Wainwright”) as sales agent, dated July 17, 2025 (the “Sales Agreement”), pursuant to which the Company may sell shares of common stock with an aggregate offering price of up to $10.39 million. We previously had an ATM program with Virtu Americas LLC (the “Virtu ATM”), which was terminated effective as of July 12, 2025. As of June 30, 2025, we cumulatively issued approximately 1.6 million shares of common stock under the Virtu ATM, at an average price of $3.84 per share. Gross proceeds totaled approximately $6.1 million and net cash proceeds was approximately $5.9 million.

The Company is currently subject to the SEC’s “baby shelf rules,” which prohibit companies with a public float of less than $75 million from issuing securities under a shelf registration statement in excess of one-third of such company’s public float in a 12-month period. These rules may limit future issuances of shares by the Company under our “shelf” registration statement on Form S-3, including through the ATM program with Wainwright or other securities offerings.

Warrants and Pre-Funded Warrants 

The following table summarizes the activity and outstanding balance of our outstanding warrants and pre-funded warrants as of June 30, 2025, along with the associated weighted average exercise price and weighted average remaining life for such warrants and pre-funded warrants.  

	Warrants						Pre-Funded Warrants(1)
(in thousands, except per share data)	Number		Wtd. Avg. Exercise Price	Wtd. Avg. Remaining Life (in years)		Aggregate Intrinsic Value	Number		Wtd. Avg. Exercise Price		Aggregate Intrinsic Value
Beginning Balance	21,295	$	1.0535	4.74	$	8,230	4,499	$	0.0001	$	6,478
Granted	—		—				—		—
Exercised	(23)		1.0500				(1,703)		0.0001
Forfeited/Expired	—		—				—		—
Outstanding at Period End	21,272	$	1.0535	4.24	$	—	2,796	$	0.0001	$	1,565
(1) Pre-funded warrants have no expiration date and only expire when exercised in full.

Refer to the Company’s Annual Report on Form 10-K for the year ended December 31, 2024 for details related to our outstanding warrants and pre-funded warrants.

Equity Incentive Plan

On June 17, 2021, the Company's stockholders approved and the Company adopted the ClearSign Technologies Corporation 2021 Equity Incentive Plan (the “2021 Plan”) which permits the Company to grant incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock, restricted stock units, performance units, and performance shares, to eligible participants, which includes employees, directors and consultants. The Board’s Human Capital and Compensation Committee (the “Compensation Committee”) is authorized to administer the 2021 Plan.

The 2021 Plan provides for an annual increase in available shares equal to the lesser of (i) 10% of the aggregate number of shares of common stock issued by the Company in the prior fiscal year; or (ii) such number provided by the

Compensation Committee; provided, however, that the total cumulative increase in the number of shares available for issuance pursuant to this automatic share increase shall not exceed 400 thousand shares of common stock. In 2025, the Board did not exercise their right to limit the automatic increase. Accordingly, the 2021 Plan share reserve increased by 400 thousand shares.

Ending balances for the 2021 Plan is as follows:

	June 30,	December 31,
(in thousands)	2025	2024
Outstanding options and restricted stock units	3,474	3,316
Reserved but unissued shares under the Plan	1,692	1,858
Reserved but unissued shares at end of period	5,166	5,174

Stock Options

Under the terms of the 2021 Plan, incentive stock options and nonstatutory stock options must have an exercise price at or above the fair market value on the date of the grant. At the time of grant, the Company will determine the period within which the option may be exercised and will specify any conditions that must be satisfied before the option vests and may be exercised. The Company estimates the fair value of stock options on the date of grant using the Black-Scholes option pricing model.

As permitted by SEC Staff Accounting Bulletin 107, management utilized the simplified approach to estimate the expected term of the options, which represents the period of time that options granted are expected to be outstanding. Expected volatility has been determined through the Company’s historical stock price volatility. The Company has not made an estimate of forfeitures at the time of the grant, but rather accounts for forfeitures at the time they occur. The risk-free rate for periods within the expected life of the option is based on the U.S. Treasury yield in effect at the time of grant. The Company has never declared or paid dividends and has no plans to do so in the foreseeable future.

Equity Incentive Plan Options

Compensation expense associated with stock option awards for the three and six months ended June 30, 2025 totaled $17 thousand and $38 thousand, respectively. Compensation expense associated with stock option awards for the three and six months ended June 30, 2024 totaled $28 thousand and $50 thousand, respectively.

A summary of the Company’s 2011 Equity Incentive Plan and the 2021 Plan stock option activity and changes is as follows:

	June 30,
	2025
(in thousands, except per share data)	Options to Purchase Common Stock	Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value
Outstanding at beginning of year	2,452	$	2.04	4.92	$	496
Granted	—	$	—
Exercised	—	$	—
Forfeited/Expired	(55)	$	2.56
Outstanding at end of period	2,397	$	2.03	4.18	$	—
Exercisable at end of period	1,872	$	1.70	3.78	$	—

The intrinsic value is the difference between the Company’s common stock price and the option exercise prices multiplied by the number of in-the-money options. This amount changes based on the fair value of the Company’s common stock.

At June 30, 2025, there was $249 thousand of total unrecognized compensation cost related to non-vested stock option-based compensation arrangements. Vesting criteria ranges from time-based to performance-based. The Company records costs for time-based arrangements ratably across the timeframe, whereas performance-based arrangements require management to continually evaluate predetermined goals against actual circumstances. The maximum contractual term for these options are ten years from the grant date.

Inducement Options

During the year ended December 31, 2023, the Company granted non-qualified stock options to its Chief Technology Officer to purchase an aggregate of 150 thousand shares of common stock with an exercise price of $0.91 as a material inducement to accept employment with the Company. These inducement options vest in three equal installments, with one third of the option vesting on the grant date, and each remaining third vesting on the second and third anniversaries of the grant date, subject to continued employment with the Company. The fair value of these options were estimated on the grant date using the Black-Scholes valuation model, which resulted in $112 thousand. The compensation expense recognized for these awards for the three and six months ended June 30, 2025 was $9 thousand and $18 thousand, respectively. The compensation expense recognized for these awards for the three and six months ended June 30, 2024 was $10 thousand and $19 thousand, respectively. Total unrecognized compensation expense for these inducement options as of June 30, 2025 was $13 thousand.

These inducement options were granted outside of the 2021 Plan and in accordance with the employment inducement

exemption provided under Nasdaq Listing Rule 5635(c)(4).

A summary of the Company’s inducement option activity and changes is as follows:

	June 30,
	2025
(in thousands, except per share data)	Options to Purchase Common Stock	Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value
Outstanding at beginning of year	491	$	1.53	3.04	$	119
Granted	—	$	—
Exercised	—	$	—
Forfeited/Expired	—	$	—
Outstanding at end of period	491	$	1.53	2.55	$	—
Exercisable at end of period	441	$	1.60	2.79	$	—

Restricted Stock Units

The Company awards employees and directors restricted stock units (“RSUs”) in lieu of cash payment for compensation. These awards are granted from the 2021 Plan. Employee vesting criteria is time based, and compensation expense is recognized ratably across the timeframe. The Company pays payroll withholding taxes on behalf of the employee at vesting, and withholds shares from the employee’s award to cover the taxes payable. The Company accrued taxes for RSU share-based compensation of $18 thousand and $29 thousand for the six months ended June 30, 2025 and 2024, respectively. Total unrecognized compensation expense for employee RSUs as of June 30, 2025 was $266 thousand.

Director vesting criteria is contingent upon the occurrence of one of four future events, which the Company cannot predict or control. Therefore, compensation expense for director RSUs is not recognized until one of these four future events occur, which is in accordance with FASB Accounting Standards Codification (“ASC”) Topic 718, “Compensation – Stock Compensation.” Total unrecognized compensation expense for director services as of June 30, 2025 was $743 thousand. Director compensation is earned on a quarterly basis with the target value of compensation set at approximately $75 thousand per quarter, assuming five directors, one chairperson for each committee and two committee members for each of the three committees. As of June 30, 2025, we had seven directors.

On May 27, 2025, David M. Maley notified the Company that he would not stand for re-election as a director of the Company upon the expiration of his current term, which expired at the Company’s 2025 annual meeting of stockholders held on July 25, 2025. In addition, Judith S. Schrecker and Catharine M. de Lacy both resigned from the Board and its committees effective as of August 4, 2025.

A summary of the Company’s RSUs activity is as follows:

	June 30,
	2025
(in thousands, except per share data)	Number of Shares	Weighted Average Grant Date Fair Value		Weighted Average Contractual Life (in years) (1)
Nonvested at beginning of year	865	$	0.99	0.88
Granted	393	$	0.91
Vested	(121)	$	0.91
Forfeited	(60)	$	0.92
Nonvested at end of period	1,077	$	0.97	1.36

1) The weighted average contractual life calculation excludes the number of director RSUs that vest upon one of four performance events (refer to discussion above for details).

A summary of the Company’s RSU compensation expense is as follows:

	For the Three Months Ended				For the Six Months Ended
	June 30,				June 30,
(in thousands, except per share data)	2025		2024		2025			2024
Share-based compensation expense	$	34	$	306	$	66	$	342
Weighted average value per share	$	0.89	$	1.36	$	0.89	$	1.32

Stock Awards

The Company awards employees stock in lieu of cash payment for compensation, typically to satisfy accrued bonus compensation. The awards are granted from the 2021 Plan.

	2025					2024
(in thousands, except per share data)	Number of Shares	Fair Value		Weighted Average per Share		Number of Shares	Fair Value		Weighted Average per Share
Fair value of stock payments in accrued compensation	326	$	279	$	0.85	307	$	326	$	1.06

Consultant Stock Plan

The Company’s 2013 Consultant Stock Plan (the “Consultant Plan”) provides for the granting of shares of common stock to consultants who provide services related to capital raising, investor relations, and making a market in or promoting the Company’s securities. The Company’s officers, employees, and Board members are not entitled to receive grants from the Consultant Plan. The Compensation Committee is authorized to administer the Consultant Plan and establish the grant terms. The Consultant Plan provides for quarterly increases in the available number of authorized shares equal to the lesser of 1% of any new shares issued by the Company during the quarter immediately prior to the adjustment date or such lesser amount as the Board shall determine.

The Consultant Plan activity is as follows:

	June 30,
(in thousands)	2025
Reserved but unissued shares at beginning of period		264
Increases in the number of authorized shares		21
Grants		(7)
Reserved but unissued shares at end of period		278

The Consultant Plan compensation expense is summarized as follows:

	For the Three Months Ended				For the Six Months Ended
	June 30,				June 30,
(in thousands, except per share data)	2025		2024		2025		2024
Share-based compensation expense	$	3	$	3	$	7	$	6
Weighted average value per share	$	0.94	$	0.81	$	0.94	$	0.81

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Net Loss per Common Share

6 Months Ended

Jun. 30, 2025

Net Loss per Common Share

Net Loss per Common Share

Note 8 – Net Loss per Common Share

The Company calculates net loss per common share in accordance with ASC Topic 260, “Earnings Per Share” (“ASC 260”). Basic and diluted net loss per common share was determined by dividing net loss applicable to common stockholders by the weighted average number of shares of common stock outstanding during the period. Under ASC 260, shares issuable for little or no cash consideration are considered outstanding common shares and included in the computation of basic net loss per share. As such, for the three and six months ended June 30, 2025 and 2024, the Company included its outstanding pre-funded warrants in its computation of net loss per share. The pre-funded warrants were issued in April and June 2024 and are each exercisable into one share of common stock at an exercise price of $0.0001 per share.

The following potentially dilutive securities have not been included in the computation of diluted net loss per share for the three and six months ended June 30, 2025 and 2024, as the result would be anti-dilutive:

	June 30,	June 30,
(in thousands)	2025	2024
Stock Options	2,888	3,148
Restricted Stock Units	1,077	682
Warrants	21,272	21,319
Total shares excluded from calculation	25,237	25,149

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Commitments and Contingencies

6 Months Ended

Jun. 30, 2025

Commitments and Contingencies.

Commitments and Contingencies

Note 9 – Commitments and Contingencies

Litigation

From time to time the Company may become involved in various lawsuits and legal proceedings which arise in the ordinary course of business. Litigation is subject to inherent uncertainties and an adverse result in any such matter may harm the Company’s business. As of the date of this report, the Company is not a party to any material pending legal proceedings or claims that the Company believes will have a material adverse effect on the business, financial condition or operating results.

Indemnification Agreements

The Company maintains indemnification agreements with our directors and officers that may require the Company to indemnify these individuals against liabilities that arise by reason of their status or service as directors or officers, except as prohibited by law.

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Government Assistance

6 Months Ended

Jun. 30, 2025

Government Assistance

Government Assistance

Note 10 – Government Assistance

During 2022, the Company was awarded a research grant from the Department of Energy (“DOE”) for approximately $250 thousand with the completion of such grant occurring in March 2023. The purpose of the grant was to produce a research paper for a flexible fuel ultra-low NOx process burner capable of burning 100% hydrogen fuel. During 2023, the Company was awarded a Phase 2 grant from the DOE to continue developing this ultra-low NOx hydrogen burner. The Phase 2 grant amount totaled approximately $1.6 million over a two-year period. These awards allow the Company to request reimbursements for expenditures such as labor, material, and administrative costs. During the three and six months ended June 30, 2025, the Company recognized $43 thousand and $91 thousand in reimbursements from the DOE, respectively. During the three and six months ended June 30, 2024, the Company recognized $168 thousand and $216 thousand in reimbursements from the DOE, respectively.

Beginning in 2021, the Company received funds relating to the Oklahoma 21^st Century Quality Jobs Act. The estimated duration of the program is up to 10 years and is designed to attract growth industries to Oklahoma. By reporting quarterly salary statistics and meeting agreed upon employment thresholds, the state remits benefit monies to the Company. During three and six months ended June 30, 2025, the Company did not receive any funds from this program. During three and six months ended June 30, 2024, the Company recognized $16 thousand and $47 thousand in government assistance from this program, respectively.

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Subsequent Events

6 Months Ended

Jun. 30, 2025

Subsequent Events

Subsequent Events

Note 11 – Subsequent Events

The Company has evaluated subsequent events as of the date of this report and has none to report.

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Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Pay vs Performance Disclosure
Net Income (Loss)	$ (1,680)	$ (1,872)	$ (3,756)	$ (2,980)

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Insider Trading Arrangements	3 Months Ended
	Jun. 30, 2025
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false
Rule 10b5-1 Arrangement Modified	false
Non-Rule 10b5-1 Arrangement Modified	false

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Summary of Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2025

Summary of Significant Accounting Policies

Basis of Presentation

Basis of Presentation

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the “SEC”) for reporting on Form 10-Q. Accordingly, certain information and footnote disclosures normally included in financial statements prepared in accordance with generally accepted accounting principles have been condensed or omitted pursuant to such rules and regulations. The condensed consolidated balance sheet at December 31, 2024 has been derived from the Company’s audited consolidated financial statements as of that date.

In the opinion of management, these condensed consolidated financial statements reflect all normal recurring and other adjustments necessary for a fair presentation. These condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2024. Operating results for interim periods are not necessarily indicative of operating results for an entire fiscal year or any other future periods.

The accompanying unaudited condensed consolidated financial statements include the accounts of ClearSign and its subsidiary. Intercompany balances and transactions have been eliminated in consolidation.

Use of Estimates

Use of Estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make certain estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Research and Development

Research and Development

The cost of research and development is expensed as incurred. Research and development costs consist of salaries, benefits, share-based compensation, consumables, and consulting fees, including costs to develop and test prototype equipment and parts. Research and development costs have been offset by funds received, if any, from strategic partners in cost sharing, collaborative projects. During the three and six months ended June 30, 2025, the Company received no funds from these types of arrangements. During the three and six months ended June 30, 2024, the Company received zero and $107 thousand, respectively, from these types of arrangements.

Foreign Operations

Foreign Operations

The accompanying unaudited condensed consolidated balance sheets as of June 30, 2025 and December 31, 2024 include assets amounting to approximately $170 thousand and $145 thousand, respectively, relating to the operations of ClearSign Asia Limited. The Beijing registered capital requirement is $350 thousand, which is required to be paid by June 30, 2032, and of which $211 thousand has been paid as of June 30, 2025. On August 22, 2024, the Board authorized management to move forward with filing for dormancy with Chinese regulators to suspend the Company’s Beijing, China operations. A dormancy filing allows the Company to keep its China legal entity in a suspended status for up to three years. The Company can revive its China operations at any time during those three years with minimal cost impact. The dormancy filing became effective as of March 12, 2025.

Recently Issued Accounting Pronouncements

Recently Issued Accounting Pronouncements

In December 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures (“ASU 2023-09”) to enhance the transparency and decision-making usefulness of income tax disclosures by requiring additional information on an entity's tax rate reconciliation, as well as income taxes paid. ASU 2023-09 is effective for our reporting period beginning January 1, 2025. We are currently assessing the impact that the adoption of ASU 2023-09 will have on the disclosures in our annual consolidated financial statements.

In November 2024, FASB issued ASU No. 2024-03, Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40) (“ASU 2024-03”). ASU 2024-03 requires enhanced disclosures about types of expenses, including purchases of inventory, employee compensation, depreciation, and amortization, in commonly presented expense captions. The amendments are effective for fiscal years beginning after December 15, 2026, and interim periods beginning after December 15, 2027, with early adoption permitted. Entities may apply the amendments prospectively or retrospectively to any or all prior periods presented in the financial statements. We are currently evaluating the impact that this guidance will have on the disclosures within our consolidated financial statements. While ASU 2024-03 will impact only our disclosures and not our financial condition and results of operations, we are assessing when we will adopt the ASU 2024-03.

In May 2025, FASB issued ASU No. 2025-04, Compensation—Stock Compensation (Topic 718) and Revenue from Contracts with Customers (Topic 606): Clarifications to Share-Based Consideration Payable to a Customer (“ASU 2025-04”), which clarifies the guidance on the accounting for share-based payment awards that are granted by an entity as consideration payable to its customer, with the intent to reduce diversity in practice and improve existing guidance by revising the definition of a “performance condition” and eliminating a forfeiture policy election for service conditions associated with share-based consideration payable to a customer. ASU 2025-04 also clarifies the guidance in Topic 606 on the variable consideration constraint does not apply to share-based consideration payable to a customer “regardless of whether an award’s grant date has occurred.” ASU 2025-04 is effective for our reporting period beginning January 1, 2027, with early adoption permitted.  We are currently assessing the impact that the adoption of ASU 2025-04 will have on the disclosures in our annual consolidated financial statements.

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Fixed Assets, Net (Tables)

6 Months Ended

Jun. 30, 2025

Fixed Assets, Net

Summary of fixed assets, net

	June 30,		December 31,
(in thousands)	2025		2024
Office furniture and equipment	$	103	$	99
Leasehold improvements		43		43
		146		142
Accumulated depreciation and amortization		(97)		(85)
		49		57
Operating lease ROU assets, net		202		181
Total	$	251	$	238

Schedule Of Supplemental balance sheet information

		June 30,			December 31,
(in thousands)		2025			2024
Operating lease ROU assets, net	$	202		$	181
Lease Liabilities:
Current lease liabilities	$	93		$	75
Long term lease liabilities		115			113
Total lease liabilities	$	208		$	188
Weighted average remaining lease term (in years):		2.2			2.6
Weighted average discount rate:		4.4	%		5.3	%

Supplemental cash flow information related to leases

	For the Six Months Ended
	June 30,
(in thousands)		2025		2024
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows used in operating leases	$	49	$	49
Non-cash impact of new leases and lease modifications
Change in operating lease liabilities	$	68	$	29
Change in operating lease ROU assets	$	68	$	32

Schedule of minimum future payments

Minimum future payments under the Company’s operating lease liabilities as of June 30, 2025 are as follows:

(in thousands)
2025 (remaining)	$	50
2026		101
2027		68
Total future lease payments		219
Less: imputed interest		(11)
	$	208

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Patents and Other Intangible Assets (Tables)

6 Months Ended

Jun. 30, 2025

Patents and Other Intangible Assets

Schedule of Patents and Other Intangible Assets

	June 30,		December 31,
(in thousands)	2025		2024
Patents
Patents pending	$	377	$	346
Issued patents		1,056		1,034
		1,433		1,380
Trademarks
Registered trademarks		86		86
		86		86
Other		8		8
		1,527		1,474
Accumulated amortization		(729)		(644)
	$	798	$	830

Schedule of future amortization expense

(in thousands)
2025 (remaining)	$	75
2026		130
2027		106
2028		70
2029		30
Thereafter		2
	$	413

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Product Warranties (Tables)

6 Months Ended

Jun. 30, 2025

Product Warranties

Summary of warranty liability activity

	June 30,		December 31,
(in thousands)	2025		2024
Warranty liability at beginning of year	$	471	$	110
Accruals		46		478
Payments		(162)		(114)
Changes related to expirations and settlements		(24)		(3)
Warranty liability at end of period	$	331	$	471

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Equity (Tables)

6 Months Ended

Jun. 30, 2025

Summary of warrants outstanding

	Warrants						Pre-Funded Warrants(1)
(in thousands, except per share data)	Number		Wtd. Avg. Exercise Price	Wtd. Avg. Remaining Life (in years)		Aggregate Intrinsic Value	Number		Wtd. Avg. Exercise Price		Aggregate Intrinsic Value
Beginning Balance	21,295	$	1.0535	4.74	$	8,230	4,499	$	0.0001	$	6,478
Granted	—		—				—		—
Exercised	(23)		1.0500				(1,703)		0.0001
Forfeited/Expired	—		—				—		—
Outstanding at Period End	21,272	$	1.0535	4.24	$	—	2,796	$	0.0001	$	1,565
(1) Pre-funded warrants have no expiration date and only expire when exercised in full.

Schedule of outstanding, reserved and authorized shares under share-based compensation plans

	June 30,	December 31,
(in thousands)	2025	2024
Outstanding options and restricted stock units	3,474	3,316
Reserved but unissued shares under the Plan	1,692	1,858
Reserved but unissued shares at end of period	5,166	5,174

Schedule of stock option activity

	June 30,
	2025
(in thousands, except per share data)	Options to Purchase Common Stock	Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value
Outstanding at beginning of year	2,452	$	2.04	4.92	$	496
Granted	—	$	—
Exercised	—	$	—
Forfeited/Expired	(55)	$	2.56
Outstanding at end of period	2,397	$	2.03	4.18	$	—
Exercisable at end of period	1,872	$	1.70	3.78	$	—

Schedule of restricted stock unit activity

	June 30,
	2025
(in thousands, except per share data)	Number of Shares	Weighted Average Grant Date Fair Value		Weighted Average Contractual Life (in years) (1)
Nonvested at beginning of year	865	$	0.99	0.88
Granted	393	$	0.91
Vested	(121)	$	0.91
Forfeited	(60)	$	0.92
Nonvested at end of period	1,077	$	0.97	1.36

Schedule of share-based compensation activity

	June 30,
(in thousands)	2025
Reserved but unissued shares at beginning of period		264
Increases in the number of authorized shares		21
Grants		(7)
Reserved but unissued shares at end of period		278

Restricted Stock Units

Schedule of compensation expense

	For the Three Months Ended				For the Six Months Ended
	June 30,				June 30,
(in thousands, except per share data)	2025		2024		2025			2024
Share-based compensation expense	$	34	$	306	$	66	$	342
Weighted average value per share	$	0.89	$	1.36	$	0.89	$	1.32

Equity Incentive Plan

Schedule of compensation expense

	2025					2024
(in thousands, except per share data)	Number of Shares	Fair Value		Weighted Average per Share		Number of Shares	Fair Value		Weighted Average per Share
Fair value of stock payments in accrued compensation	326	$	279	$	0.85	307	$	326	$	1.06

Consultant Stock Plan

Schedule of compensation expense

	For the Three Months Ended				For the Six Months Ended
	June 30,				June 30,
(in thousands, except per share data)	2025		2024		2025		2024
Share-based compensation expense	$	3	$	3	$	7	$	6
Weighted average value per share	$	0.94	$	0.81	$	0.94	$	0.81

Non-Qualified Stock Option

Schedule of stock option activity

	June 30,
	2025
(in thousands, except per share data)	Options to Purchase Common Stock	Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value
Outstanding at beginning of year	491	$	1.53	3.04	$	119
Granted	—	$	—
Exercised	—	$	—
Forfeited/Expired	—	$	—
Outstanding at end of period	491	$	1.53	2.55	$	—
Exercisable at end of period	441	$	1.60	2.79	$	—

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Net Loss per Common Share (Tables)

6 Months Ended

Jun. 30, 2025

Net Loss per Common Share

Schedule of potentially dilutive securities that have not been included in the computation of diluted net loss per share

	June 30,	June 30,
(in thousands)	2025	2024
Stock Options	2,888	3,148
Restricted Stock Units	1,077	682
Warrants	21,272	21,319
Total shares excluded from calculation	25,237	25,149

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Organization and Description of Business - Business Segments (Details) - segment	3 Months Ended	6 Months Ended
	Jun. 30, 2025	Jun. 30, 2025
Organization and Description of Business
Number of operating segment		1
Number of reportable segment		1
Revenue from Contract with Customer Benchmark | Geographic Concentration Risk [Member] | UNITED STATES
Organization and Description of Business
Concentration risk percentage	100.00%	100.00%

XML

Organization and Description of Business (Details)	Aug. 22, 2024
Suspended status | ClearSign Asia Limited
Organization and Description of Business
Suspended status, period	3 years

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Summary of Significant Accounting Policies - Research and Development, and Government Assistance (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Summary of Significant Accounting Policies
Research and Development, funding received to offset costs	$ 0	$ 0	$ 0	$ 107

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Summary of Significant Accounting Policies - Foreign Operations (Details) - USD ($) $ in Thousands	Aug. 22, 2024	Jun. 30, 2025	Dec. 31, 2024
Property, Plant and Equipment [Line Items]
Assets		$ 14,231	$ 15,916
ClearSign Asia Limited | Suspended status
Property, Plant and Equipment [Line Items]
Suspended status, period	3 years
ClearSign Asia Limited
Property, Plant and Equipment [Line Items]
Assets		170	$ 145
Registered capital requirement		350
Capital requirement paid		$ 211
ClearSign Asia Limited | ClearSign Asia Limited | Suspended status
Property, Plant and Equipment [Line Items]
Suspended status, period	3 years

XML

Fixed Assets, Net - Summary (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Fixed Assets, Net
Office furniture and equipment	$ 103		$ 103		$ 99
Leasehold improvements	43		43		43
Fixed assets, gross	146		146		142
Accumulated depreciation and amortization	(97)		(97)		(85)
Fixed assets, net, after accumulated amortization	49		49		57
Operating lease ROU assets, net	202		202		181
Total	251		251		$ 238
Depreciation expense	$ 7	$ 4	$ 12	$ 11

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Fixed Assets, Net - Leases (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended		6 Months Ended
	May 31, 2025	Oct. 31, 2024	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Leases
Increase (decrease) in operating lease right of use asset					$ 68
Short term lease expense			$ 5	$ 5	11	$ 11
Monthly rent expense					10
Operating lease cost			$ 25	$ 24	$ 49	$ 48
CHINA
Leases
Renewal option term	24 months
Short term monthly rent expense	$ 3
Seattle [Member]
Leases
Short term monthly rent expense		$ 2
Agreement expiration term (in years)		12 months
Tulsa [Member]
Leases
Annual rent expense, increase (in percent)					2.00%
Minimum
Leases
Remaining term (in years)		2 years
Maximum
Leases
Remaining term (in years)		3 years

XML

Fixed Assets, Net - Leases - Supplemental balance sheet and cash flow information (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Operating Lease
Operating lease ROU assets, net	$ 202		$ 181
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Property, Plant and Equipment, Net		Property, Plant and Equipment, Net
Lease Liabilities:
Current lease liabilities	$ 93		$ 75
Long term lease liabilities	115		113
Total lease liabilities	$ 208		$ 188
Weighted average remaining lease term (in years)	2 years 2 months 12 days		2 years 7 months 6 days
Weighted average discount rate	4.40%		5.30%
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows used in operating leases	$ 49	$ 49
Change in operating lease liabilities	68	29
Change in operating lease ROU assets	$ 68	$ 32

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Fixed Assets, Net - Minimum future lease payments (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Fixed Assets, Net
2025 (remaining)	$ 50
2026	101
2027	68
Total future lease payments	219
Less: imputed interest	(11)
Total payment due under lease agreement	$ 208	$ 188

XML

Patents and Other Intangible Assets - Summary (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Patents	$ 1,433	$ 1,380
Trademarks	86	86
Other	8	8
Patents and other intangible assets	1,527	1,474
Accumulated amortization	(729)	(644)
Finite-Lived Intangible Assets, Net	798	830
Patents pending
Patents	377	346
Issued patents
Patents	1,056	1,034
Registered trademarks
Trademarks	$ 86	$ 86

XML

Patents and Other Intangible Assets - Future amortization expense (Details) $ in Thousands	Jun. 30, 2025 USD ($)
Patents and Other Intangible Assets
2025 (remaining)	$ 75
2026	130
2027	106
2028	70
2029	30
Thereafter	2
Finite-Lived Intangible Assets, Net	$ 413

XML

Patents and Other Intangible Assets - Additional information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Intangible assets
Amortization expense	$ 43	$ 42	$ 85	$ 80
Minimum
Intangible assets
Amortization life (in years)	3 years		3 years
Maximum
Intangible assets
Amortization life (in years)	5 years		5 years
Trademarks
Intangible assets
Amortization life (in years)	10 years		10 years

XML

Revenue, Contract Assets and Contract Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Revenue, Contract Assets and Contract Liabilities
Revenues	$ 133	$ 45	$ 534	$ 1,147
Cost of goods sold	78	$ 3	283	$ 668
Contract assets	268		268		$ 194
Contract liabilities	1,675		1,675		$ 73
Revenue recognized	$ 10		$ 33

XML

Product Warranties (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2025	Dec. 31, 2024
Product Warranties
Warranty liability at beginning of year	$ 471	$ 110
Accruals	46	478
Payments	(162)	(114)
Changes related to expirations and settlements	(24)	(3)
Warranty liability at end of period	$ 331	$ 471

XML

Equity - Common Stock and Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended
	Jul. 17, 2025	Jun. 30, 2024	Jun. 30, 2025	Dec. 31, 2024
Stockholders' equity
Common stock, authorized shares			87,500,000	87,500,000
Preferred stock, authorized shares			2,000,000	2,000,000
ATM | Subsequent events
Stockholders' equity
Aggregate offering price	$ 10,390
Common Stock | ATM
Stockholders' equity
Number of shares issued to date			1,600,000
Share price of shares issued in offering (in dollars per share)			$ 3.84
Gross proceeds to date			$ 6,100
Net proceeds to date			$ 5,900
Common Stock | Participation Right
Stockholders' equity
Number of shares of common stock issued		3,350,000

XML

Equity - Warrants & Pre-Funded Warrants (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2025	Dec. 31, 2024
Warrants
Stockholders' equity
Warrants Outstanding at beginning of period (in shares)	21,295
Exercised	(23)
Warrants Outstanding at end of period (in shares)	21,272	21,295
Beginning Balance	$ 1.0535
Exercised	1.05
Outstanding at Period End	$ 1.0535	$ 1.0535
Outstanding, Wtd. Avg. Remaining Life (in years)	4 years 2 months 26 days	4 years 8 months 26 days
Aggregate Intrinsic Value		$ 8,230
Pre-Funded Warrants
Stockholders' equity
Warrants Outstanding at beginning of period (in shares)	4,499
Exercised	(1,703)
Warrants Outstanding at end of period (in shares)	2,796	4,499
Beginning Balance	$ 0.0001
Exercised	0.0001
Outstanding at Period End	$ 0.0001	$ 0.0001
Aggregate Intrinsic Value	$ 1,565	$ 6,478

XML

Equity - 2021 Equity Incentive Plan (Details) - 2021 Plan - shares shares in Thousands	6 Months Ended
	Jun. 30, 2025	Dec. 31, 2024
Share-based compensation
Maximum number of shares that may be issued as a proportion of outstanding stock	10.00%
Maximum increase in number of shares available for issuance	400
Increase in share reserve	400
Outstanding options and restricted stock units	3,474	3,316
Reserved but unissued shares under the Plan	1,692	1,858
Total authorized shares under the Plan	5,166	5,174

XML

Equity - Equity Incentive Plan Options and Inducement Options (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Equity Incentive Plan
Share-based compensation
Outstanding shares, beginning balance			2,452
Forfeited/Expired (in shares)			(55)
Outstanding shares, ending balance	2,397		2,397		2,452
Exercisable (in shares)	1,872		1,872
Outstanding - Weighted Average Exercise Price (in dollars per share)			$ 2.04
Forfeited/Expired - Weighted Average Exercise Price (in dollars per share)			2.56
Outstanding - Weighted Average Exercise Price (in dollars per share)	$ 2.03		2.03		$ 2.04
Exercisable - Weighted Average Exercise Price (in dollars per share)	$ 1.7		$ 1.7
Outstanding - Weighted Average Remaining Contractual Life (in years)			4 years 2 months 4 days		4 years 11 months 1 day
Exercisable - Weighted Average Remaining Contractual Life (in years)			3 years 9 months 10 days
Aggregate Intrinsic Value, Outstanding beginning of year			$ 496
Aggregate Intrinsic Value, Outstanding end of period					$ 496
Total unrecognized compensation	$ 249		$ 249
Contractual life			10 years
Non-Qualified Stock Option
Share-based compensation
Outstanding shares, beginning balance			491
Outstanding shares, ending balance	491		491		491
Exercisable (in shares)	441		441
Outstanding - Weighted Average Exercise Price (in dollars per share)			$ 1.53
Outstanding - Weighted Average Exercise Price (in dollars per share)	$ 1.53		1.53		$ 1.53
Exercisable - Weighted Average Exercise Price (in dollars per share)	$ 1.6		$ 1.6
Outstanding - Weighted Average Remaining Contractual Life (in years)			2 years 6 months 18 days		3 years 14 days
Exercisable - Weighted Average Remaining Contractual Life (in years)			2 years 9 months 14 days
Aggregate Intrinsic Value, Outstanding beginning of year			$ 119
Aggregate Intrinsic Value, Outstanding end of period					$ 119
Equity Option
Share-based compensation
Compensation expense	$ 17	$ 28	$ 38	$ 50

XML

Equity - Inducement Options (Details) - Non-Qualified Stock Option - Chief Technology Officer $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2025 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2025 USD ($)	Jun. 30, 2024 USD ($)	Dec. 31, 2023 USD ($) installment $ / shares shares
Share-based compensation
Grants of stock options | shares					150
Exercise price (in dollars per share) | $ / shares					$ 0.91
Number of installments | installment					3
Vesting percentage					33.00%
Fair value of options granted (in dollars)					$ 112
Share based compensation cost related to vesting awards	$ 9	$ 10	$ 18	$ 19
Total unrecognized compensation	$ 13		$ 13

XML

Equity - Restricted Stock Units (Details) - Restricted Stock Units - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024
Director
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Target value of compensation per quarter	$ 75
Unrecognized compensation expense for director services	743
Share-Based Payment Arrangement, Employee [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Unrecognized compensation expense	266
Reserve for share-based compensation tax withholdings	$ 18	$ 29

XML

Equity - Restricted Stock units Activity (Details) - Restricted Stock Units - $ / shares shares in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2025	Dec. 31, 2024
Number of Shares
Nonvested at beginning of year	865
Granted	393
Vested	(121)
Forfeited	(60)
Nonvested at end of period	1,077	865
Weighted Average Grant Date Fair Value
Nonvested at beginning of year	$ 0.99
Granted	0.91
Vested	0.91
Forfeited	0.92
Nonvested at end of period	$ 0.97	$ 0.99
Weighted Average Remaining Contractual Life, Nonvested	1 year 4 months 9 days	10 months 17 days

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Equity - Restricted Stock Units - Compensation Expense (Details) - Restricted Stock Units - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share-based compensation expense	$ 34	$ 306	$ 66	$ 342
Weighted average value per share	$ 0.89	$ 1.36	$ 0.89	$ 1.32

XML

Equity - Stock Awards (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Jun. 30, 2025	Jun. 30, 2024
Equity
Fair value of stock payments in accrued compensation, Number of Shares			326	307
Fair value of stock payments in accrued compensation, Fair Value	$ 279	$ 326	$ 279	$ 326
Fair value of stock payments in accrued compensation, Weighted Average per Share			$ 0.85	$ 1.06

XML

Equity - Consultant Stock Plan (Details) - Consultant Stock Plan - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Maximum increase in available number of authorized shares as a percentage of new shares issued			1.00%
Reserved but unissued shares at beginning of year			264
Increases in the number of authorized shares			21
Grants			(7)
Reserved but unissued shares at end of year	278		278
Share-based compensation expense	$ 3	$ 3	$ 7	$ 6
Weighted average value per share	$ 0.94	$ 0.81	$ 0.94	$ 0.81

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Net Loss per Common Share (Details) - $ / shares shares in Thousands	6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Apr. 30, 2024
Net Loss Per Common Share
Total shares excluded from calculation	25,237	25,149
Private Pre-Funded Warrants | Private Placement
Net Loss Per Common Share
Exercise price (in dollars per share)		$ 0.0001	$ 0.0001
Employee Stock Option
Net Loss Per Common Share
Total shares excluded from calculation	2,888	3,148
Restricted Stock Units
Net Loss Per Common Share
Total shares excluded from calculation	1,077	682
Warrants
Net Loss Per Common Share
Total shares excluded from calculation	21,272	21,319

XML

Government Assistance (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Government Assistance [Line Items]
Government assistance	$ 43	$ 185	$ 91	$ 264
Research Grant From the Department of Energy
Government Assistance [Line Items]
Total award					$ 1,600	$ 250
Duration of the program					2 years
Government assistance	43	168	91	216
Oklahoma Quality Jobs Act
Government Assistance [Line Items]
Duration of the program							10 years
Government assistance	$ 0	$ 16	$ 0	$ 47