Business Segment and Geographic Financial Data - Reporting Segment Net Sales and Gross Margin (Details) - USD ($)	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Revenues from external customers	$ 11,847,000	$ 9,741,000	$ 24,638,000	$ 18,232,000
Cost of sales	(8,125,000)	(6,116,000)	(15,891,000)	(10,885,000)
Gross margin	3,722,000	3,625,000	8,747,000	7,347,000
Selling, general and administrative	(4,763,000)	(5,923,000)	(9,684,000)	(11,077,000)
Restructuring charge	0	(58,000)	0	(119,000)
Research and development	(261,000)	(280,000)	(549,000)	(564,000)
Intangible assets abandonment	(317,000)		(317,000)
Building impairment		(2,965,000)		(2,965,000)
Operating loss from continuing operations	(1,619,000)	(5,601,000)	(1,803,000)	(7,378,000)
Air Pollution Control Segment
Segment Reporting Information [Line Items]
Revenues from external customers	8,407,000	5,545,000	16,990,000	9,547,000
Cost of sales	(6,328,000)	(4,103,000)	(11,924,000)	(6,603,000)
Gross margin	2,079,000	1,442,000	5,066,000	2,944,000
Selling, general and administrative	0	0	0	0
Restructuring charge		(58,000)		(58,000)
Research and development	0	0	0	0
Operating loss from continuing operations	2,079,000	1,384,000	5,066,000	2,886,000
FUEL CHEM Segment
Segment Reporting Information [Line Items]
Revenues from external customers	3,440,000	4,196,000	7,648,000	8,685,000
Cost of sales	(1,797,000)	(2,013,000)	(3,967,000)	(4,282,000)
Gross margin	1,643,000	2,183,000	3,681,000	4,403,000
Selling, general and administrative	0	0	0	0
Restructuring charge		0		(61,000)
Research and development	0	0	0	0
Operating loss from continuing operations	1,643,000	2,183,000	3,681,000	4,342,000
Other
Segment Reporting Information [Line Items]
Selling, general and administrative	(4,763,000)	(5,923,000)	(9,684,000)	(11,077,000)
Restructuring charge		0		0
Research and development	(261,000)	(280,000)	(549,000)	(564,000)
Intangible assets abandonment	(317,000)		(317,000)
Building impairment		(2,965,000)		(2,965,000)
Operating loss from continuing operations	$ (5,341,000)	$ (9,168,000)	$ (10,550,000)	$ (14,606,000)

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The aggregate cost of goods produced and sold and services rendered during the reporting period.

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