Business Segment and Geographic Disclosures (Detail) - Reporting Segment Net Sales and Gross Margin (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Revenues from external customers	$ 20,190	$ 29,092	$ 38,851	$ 51,576
Cost of sales	(11,677)	(17,227)	(22,487)	(30,279)
Gross margin	8,513	11,865	16,364	21,297
Selling, general and administrative	(8,959)	(9,307)	(17,703)	(17,765)
Research and development	(225)	(430)	(469)	(1,363)
Operating (loss) income	(671)	2,128	(1,808)	2,169
Air Pollution Control Segment
Revenues from external customers	11,304	20,239	22,038	33,186
Cost of sales	(7,688)	(13,083)	(14,718)	(21,666)
Gross margin	3,616	7,156	7,320	11,520
Selling, general and administrative		0	0	0
Research and development		0	0	0
Operating (loss) income	3,616	7,156	7,320	11,520
FUEL CHEM Segment
Revenues from external customers	8,886	8,853	16,813	18,390
Cost of sales	(3,989)	(4,144)	(7,769)	(8,613)
Gross margin	4,897	4,709	9,044	9,777
Selling, general and administrative		0	0	0
Research and development		0	0	0
Operating (loss) income	4,897	4,709	9,044	9,777
Other
Revenues from external customers		0	0	0
Cost of sales		0	0	0
Gross margin		0	0	0
Selling, general and administrative	(8,959)	(9,307)	(17,703)	(17,765)
Research and development	(225)	(430)	(469)	(1,363)
Operating (loss) income	$ (9,184)	$ (9,737)	$ (18,172)	$ (19,128)

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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The net result for the period of deducting operating expenses from operating revenues.

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No definition available.

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- Definition

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 985

-SubTopic 20

-Section 50

-Paragraph 1

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 730

-SubTopic 10

-Section 50

-Paragraph 1

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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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- Definition

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.

+ References

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)

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 4

-Article 5

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 330

-SubTopic 10

-Section 30

-Paragraph 8

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