Revenue (Tables)

3 Months Ended

Mar. 31, 2019

Revenue from Contract with Customer [Abstract]

Disaggregation of Revenue

The following table presents the timing of our revenue recognition:

	Three Months Ended   March 31,
	2019	2018
Products transferred at a point in time	5,414	5,069
Products and services transferred over time	4,741	7,722
Total Revenues	10,155	12,791

The following table presents our revenues disaggregated by product technology:

	Three Months Ended   March 31,
	2019		2018
Air Pollution Control
Technology solutions	$	4,741	$	7,722
Spare parts	149		300
Ancillary revenue	899		561
Total Air Pollution Control Technology revenues	5,789		8,583
FUEL CHEM
FUEL CHEM technology solutions	4,366		4,208
Total Revenues	$	10,155	$	12,791

Revenue Disaggregated by Geography

The following table presents our revenues disaggregated by geography, based on the billing addresses of our customers:

	Three Months Ended   March 31,
	2019		2018
United States	$	8,815	$	10,242
Foreign Revenues
South America	175		335
Europe	617		1,454
Asia	548		760
Total Foreign Revenues	1,340		2,549
Total Revenues	$	10,155	$	12,791