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

9 Months Ended

Sep. 30, 2023

Notes Tables

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

	Air Pollution			FUEL CHEM
Three months ended September 30, 2023	Control Segment			Segment			Other			Total
Revenues from external customers	$	3,711		$	4,277		$	—		$	7,988
Cost of sales		(2,214	)		(2,162	)		—			(4,376	)
Gross margin		1,497			2,115			—			3,612
Selling, general and administrative		—			—			(2,966	)		(2,966	)
Research and development		—			—			(513	)		(513	)
Operating income (loss) from operations	$	1,497		$	2,115		$	(3,479	)	$	133

	Air Pollution			FUEL CHEM
Three months ended September 30, 2022	Control Segment			Segment			Other			Total
Revenues from external customers	$	2,728		$	5,289		$	—		$	8,017
Cost of sales		(1,801	)		(2,544	)		—			(4,345	)
Gross margin		927			2,745			—			3,672
Selling, general and administrative		—			—			(3,273	)		(3,273	)
Research and development		—			—			(207	)		(207	)
Operating income (loss) from operations	$	927		$	2,745		$	(3,480	)	$	192

	Air Pollution			FUEL CHEM
Nine months ended September 30, 2023	Control Segment			Segment			Other			Total
Revenues from external customers	$	10,692		$	10,044		$	—		$	20,736
Cost of sales		(7,155	)		(5,168	)		—			(12,323	)
Gross margin		3,537			4,876			—			8,413
Selling, general and administrative		—			—			(9,126	)		(9,126	)
Research and development		—			—			(1,144	)		(1,144	)
Operating income (loss) from operations	$	3,537		$	4,876		$	(10,270	)	$	(1,857	)

	Air Pollution			FUEL CHEM
Nine months ended September 30, 2022	Control Segment			Segment			Other			Total
Revenues from external customers	$	7,670		$	12,250		$	—		$	19,920
Cost of sales		(5,032	)		(6,248	)		—			(11,280	)
Gross margin		2,638			6,002			—			8,640
Selling, general and administrative		—			—			(9,201	)		(9,201	)
Research and development		—			—			(716	)		(716	)
Operating income (loss) from operations	$	2,638		$	6,002		$	(9,917	)	$	(1,277	)

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

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2023		2022		2023		2022
Revenues:
United States	$	5,640	$	6,972	$	15,937	$	14,939
Foreign		2,348		1,045		4,799		4,981
	$	7,988	$	8,017	$	20,736	$	19,920

	September 30,		December 31,
	2023		2022
Assets:
United States	$	46,550	$	47,007
Foreign		3,769		3,117
	$	50,319	$	50,124