||Development and Fabrication of a Prototype Fibrous Aerosol Monitor (FAM).
Lilienfeld, Pedro ;
Elterman., Paul B. ;
||GCA Corp., Bedford, Mass. GCA Technology Div.;National Inst. for Occupational Safety and Health, Cincinnati, Ohio. Div. of Physical Sciences and Engineering.;Environmental Protection Agency, Washington, D.C. Office of Energy, Minerals and Industry.
||PHS-NIOSH-210-76-0110; DHEW/PUB/NIOSH-78/125 ; EPA/600/7-77/147
Gas detectors ;
Optical equipment ;
Glass fibers ;
Design criteria ;
Performance evaluation ;
Light scattering ;
Air pollution ;
Air pollution detection
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This report describes a program whose objective was to develop, design, fabricate and laboratory-test two prototype instruments capable of real-time selective detection and measurement of airborne fibrous-shaped particles. The selective detection of the fibers is effected by synchronous detection of the resulting modulation of the light scattered from a continuous-wave helium-neon laser beam by the rotating particles. The theory of operation, design of the electric-optical detection configuration and the electronic signal processing method are discussed. By means of a scattering pulse sharpness discrimination technique, fibers whose length exceed a selectable value are detected and their number concentration digitally displayed. A concentration of the order of one fiber per cubic centimeter can be assessed within a relative standard deviation of 10 percent with a counting period of 10 minutes. The FAM is a portable, battery-powered instrument capable of operating continuously for about 4 hours between battery charges. Preliminary tests with crocidolite and crysotile asbestos as well as with glass fibers were performed in the laboratory and the results indicate good correlation with the standard NIOSH phase contrast microscopy filter counting method.