Business Segment and Geographic Financial Data (Detail) - Reporting Segment Net Sales and Gross Margin - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Revenues from external customers	$ 15,175	$ 18,683	$ 32,997	$ 33,786
Cost of sales	(9,595)	(11,547)	(21,369)	(19,984)
Gross margin	5,580	7,136	11,628	13,802
Selling, general and administrative	(6,760)	(8,400)	(14,239)	(16,603)
Research and development	(1,122)	(982)	(2,280)	(1,854)
Operating (loss)	(2,302)	(2,246)	(4,891)	(4,655)
Air Pollution Control Segment
Revenues from external customers	10,031	11,087	23,021	17,944
Cost of sales	(7,152)	(7,769)	(16,471)	(12,090)
Gross margin	2,879	3,318	6,550	5,854
Selling, general and administrative	0	0	0	0
Research and development	0	0	0	0
Operating (loss)	2,879	3,318	6,550	5,854
FUEL CHEM Segment
Revenues from external customers	5,144	7,596	9,976	15,842
Cost of sales	(2,443)	(3,778)	(4,898)	(7,894)
Gross margin	2,701	3,818	5,078	7,948
Selling, general and administrative	0	0	0	0
Research and development	0	0	0	0
Operating (loss)	2,701	3,818	5,078	7,948
Fuel Conversion Segment
Selling, general and administrative	0	0
Research and development	(827)	(629)	(1,514)	(1,101)
Operating (loss)	(827)	(629)	(1,514)	(1,101)
Other
Selling, general and administrative	(6,760)	(8,400)	(14,239)	(16,603)
Research and development	(295)	(353)	(766)	(753)
Operating (loss)	$ (7,055)	$ (8,753)	$ (15,005)	$ (17,356)

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

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Aggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.

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No definition available.

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The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 730
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6420194&loc=d3e21568-108373

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 985
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6501960&loc=d3e128462-111756

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. Direct selling expenses (for example, credit, warranty, and advertising) are expenses that can be directly linked to the sale of specific products. Indirect selling expenses are expenses that cannot be directly linked to the sale of specific products, for example telephone expenses, Internet, and postal charges. General and administrative expenses include salaries of non-sales personnel, rent, utilities, communication, etc.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.4)
-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 330
-SubTopic 10
-Section 30
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=51677171&loc=d3e3636-108311

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