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

6 Months Ended

Jun. 30, 2023

Notes Tables

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

	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
Three months ended June 30, 2022	Control Segment			Segment			Other			Total
Revenues from external customers	$	2,738		$	3,630		$	—		$	6,368
Cost of sales		(1,802	)		(1,888	)		—			(3,690	)
Gross margin		936			1,742			—			2,678
Selling, general and administrative		—			—			(2,874	)		(2,874	)
Research and development		—			—			(289	)		(289	)
Operating income (loss) from operations	$	936		$	1,742		$	(3,163	)	$	(485	)

	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	)

	Air Pollution			FUEL CHEM
Six months ended June 30, 2022	Control Segment			Segment			Other			Total
Revenues from external customers	$	4,942		$	6,961		$	—		$	11,903
Cost of sales		(3,231	)		(3,704	)		—			(6,935	)
Gross margin		1,711			3,257			—			4,968
Selling, general and administrative		—			—			(5,928	)		(5,928	)
Research and development		—			—			(509	)		(509	)
Operating income (loss) from operations	$	1,711		$	3,257		$	(6,437	)	$	(1,469	)

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,
	2023		2022		2023		2022
Revenues:
United States	$	4,316	$	4,279	$	10,297	$	7,967
Foreign		1,145		2,089		2,451		3,936
	$	5,461	$	6,368	$	12,748	$	11,903

	June 30,		December 31,
	2023		2022
Assets:
United States	$	46,191	$	47,007
Foreign		3,418		3,117
	$	49,609	$	50,124