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

6 Months Ended

Jun. 30, 2022

Notes Tables

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

	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
Three months ended June 30, 2021	Control Segment			Segment			Other			Total
Revenues from external customers	$	986		$	4,232		$	—		$	5,218
Cost of sales		(507	)		(2,128	)		—			(2,635	)
Gross margin		479			2,104			—			2,583
Selling, general and administrative		—			—			(2,957	)		(2,957	)
Research and development		—			—			(315	)		(315	)
Operating income (loss) from operations	$	479		$	2,104		$	(3,272	)	$	(689	)

	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	)

	Air Pollution			FUEL CHEM
Six months ended June 30, 2021	Control Segment			Segment			Other			Total
Revenues from external customers	$	1,893		$	8,358		$	—		$	10,251
Cost of sales		(1,038	)		(4,272	)		—			(5,310	)
Gross margin		855			4,086			—			4,941
Selling, general and administrative		—			—			(6,057	)		(6,057	)
Research and development		—			—			(730	)		(730	)
Operating income (loss) from operations	$	855		$	4,086		$	(6,787	)	$	(1,846	)

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,
	2022		2021		2022		2021
Revenues:
United States	$	4,279	$	4,588	$	7,967	$	9,051
Foreign		2,089		630		3,936		1,200
	$	6,368	$	5,218	$	11,903	$	10,251

	June 30,		December 31,
	2022		2021
Assets:
United States	$	45,934	$	46,271
Foreign		3,184		3,703
	$	49,118	$	49,974