"In September 1980, an EPA-owned mobile venture scrubber was tested for control of particulate emissions from an in-situ oil shale retort operated by the Department of Energy's Laramie Energy Technology Center (LETC) in Wyoming. The entire retort off-gas flow of 15.4 m3 /min (545 acfm), saturated with moisture at a temperature of 58°C, was scrubbed with water at liquid-to-gas ratios of 1.5 to 2.4 L/m3 (11 to 18 gpm/l03 acfm), corresponding to pressure drops of 6.5 to 9.5 kPa (26 to 38 in. H2 0) . In order to quantify the effect of venturi scrubbing and to further characterize the overall air pollution potential of oil shale processing, sampling and analyses were conducted to measure not only particulate loading and size distribution, but also hydrocarbons (total, low-molecular-weight fractions, polycyclic organic matter), carbon monoxide, nitrogen oxides, carbonyl sulfide and hydrogen sulfide, ammonia, hydrogen cyanide, and trace elements. More than 50 weight percent of the particulate matter emitted by LETC's pilot oil shale retort was of a size less than four micrometers in diameter, with ten percent being sub-micrometer-sized, as determined by cascade impactor sampling. Although particulate concentrations in the scrubber inlet varied from approximately 130 to 390 milligrams ms per dry norm 1 cubic meter, the mobile control device was consistently able to achieve outlet concentrations around 3S mg/dncm. Particulate control efficiencies up to 94 percent were observed."