Note 11 - Business Segment and Geographic Financial Data (Tables)

6 Months Ended

Jun. 30, 2024

Notes Tables

Schedule of Segment Reporting Information, by Segment [Table Text Block]

	Air Pollution			FUEL CHEM
Three months ended June 30, 2024	Control Segment			Segment			Other			Total
Revenues from external customers	$	3,949		$	3,093		$	—		$	7,042
Cost of sales		(2,405	)		(1,685	)		—			(4,090	)
Gross margin		1,544			1,408			—			2,952
Selling, general and administrative		—			—			(3,245	)		(3,245	)
Research and development		—			—			(422	)		(422	)
Operating income (loss) from operations	$	1,544		$	1,408		$	(3,667	)	$	(715	)

	Air Pollution			FUEL CHEM
Three months ended June 30, 2023	Control Segment			Segment			Other			Total
Revenues from external customers	$	3,422		$	2,039		$	—		$	5,461
Cost of sales		(2,347	)		(1,118	)		—			(3,465	)
Gross margin		1,075			921			—			1,996
Selling, general and administrative		—			—			(2,915	)		(2,915	)
Research and development		—			—			(413	)		(413	)
Operating income (loss) from operations	$	1,075		$	921		$	(3,328	)	$	(1,332	)

	Air Pollution			FUEL CHEM
Six months ended June 30, 2024	Control Segment			Segment			Other			Total
Revenues from external customers	$	6,267		$	5,732		$	—		$	11,999
Cost of sales		(3,833	)		(3,185	)		—			(7,018	)
Gross margin		2,434			2,547			—			4,981
Selling, general and administrative		—			—			(6,590	)		(6,590	)
Research and development		—			—			(798	)		(798	)
Operating income (loss) from operations	$	2,434		$	2,547		$	(7,388	)	$	(2,407	)

	Air Pollution			FUEL CHEM
Six months ended June 30, 2023	Control Segment			Segment			Other			Total
Revenues from external customers	$	6,981		$	5,767		$	—		$	12,748
Cost of sales		(4,941	)		(3,006	)		—			(7,947	)
Gross margin		2,040			2,761			—			4,801
Selling, general and administrative		—			—			(6,160	)		(6,160	)
Research and development	$	—		$	—		$	(631	)	$	(631	)
Operating income (loss) from operations	$	2,040		$	2,761		$	(6,791	)	$	(1,990	)

Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block]

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2024		2023		2024		2023
Revenues:
United States	$	4,471	$	4,316	$	8,066	$	10,297
Foreign		2,571		1,145		3,933		2,451
	$	7,042	$	5,461	$	11,999	$	12,748

	June 30,		December 31,
	2024		2023
Assets:
United States	$	45,525	$	46,487
Foreign		3,469		3,901
	$	48,994	$	50,388