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

9 Months Ended

Sep. 30, 2022

Notes Tables

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

	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
Three months ended September 30, 2021	Control Segment			Segment			Other			Total
Revenues from external customers	$	1,944		$	5,615		$	—		$	7,559
Cost of sales		(1,134	)		(2,706	)		—			(3,840	)
Gross margin		810			2,909			—			3,719
Selling, general and administrative		—			—			(2,801	)		(2,801	)
Research and development		—			—			(340	)		(340	)
Operating income (loss) from operations	$	810		$	2,909		$	(3,141	)	$	578

	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	)

	Air Pollution			FUEL CHEM
Nine months ended September 30, 2021	Control Segment			Segment			Other			Total
Revenues from external customers	$	3,837		$	13,973		$	—		$	17,810
Cost of sales		(2,172	)		(6,978	)		—			(9,150	)
Gross margin		1,665			6,995			—			8,660
Selling, general and administrative		—			—			(8,858	)		(8,858	)
Research and development		—			—			(1,070	)		(1,070	)
Operating income (loss) from operations	$	1,665		$	6,995		$	(9,928	)	$	(1,268	)

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,
	2022		2021		2022		2021
Revenues:
United States	$	6,972	$	6,049	$	14,939	$	15,100
Foreign		1,045		1,510		4,981		2,710
	$	8,017	$	7,559	$	19,920	$	17,810

	September 30,		December 31,
	2022		2021
Assets:
United States	$	47,170	$	46,271
Foreign		2,512		3,703
	$	49,682	$	49,974