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

9 Months Ended

Sep. 30, 2021

Notes Tables

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

	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
Three months ended September 30, 2020	Control Segment		Segment			Other			Total
Revenues from external customers	$	2,886	$	5,269		$	—		$	8,155
Cost of sales		304		(2,553	)		—			(2,249	)
Gross margin		3,190		2,716			—			5,906
Selling, general and administrative		—		—			(3,184	)		(3,184	)
Research and development		—		—			(285	)		(285	)
Operating income (loss) from operations	$	3,190	$	2,716		$	(3,469	)	$	2,437

	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	)

	Air Pollution			FUEL CHEM
Nine months ended September 30, 2020	Control Segment			Segment			Other			Total
Revenues from external customers	$	6,019		$	10,315		$	—		$	16,334
Cost of sales		(2,782	)		(5,517	)		—			(8,299	)
Gross margin		3,237			4,798			—			8,035
Selling, general and administrative		—			—			(9,825	)		(9,825	)
Research and development		—			—			(880	)		(880	)
Operating income (loss) from operations	$	3,237		$	4,798		$	(10,705	)	$	(2,670	)

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,
	2021		2020		2021		2020
Revenues:
United States	$	6,049	$	6,473	$	15,100	$	12,880
Foreign		1,510		1,682		2,710		3,454
	$	7,559	$	8,155	$	17,810	$	16,334

	September 30,		December 31,
	2021		2020
Assets:
United States	$	46,713	$	24,524
Foreign		4,326		5,564
	$	51,039	$	30,088