PLM by OSHA ID191
In 1992, OSHA came out with a method to analyze asbestos. The method number is OSHA ID-191.
The main difference between this method and the EPA and NIOSH methods are the requirement of using a phase-polar microscope which has the polarizing ability in a phase contrast microscope. It is so required because OSHA wants the same size fibers that are visible in air filter analysis by the Phase Contrast method to be seen in the Polarized Light.
Other than the stated differences, this method is similar to the EPA 600 and NIOSH 9002 in many other ways.
The analytical procedure is first by gross examination under a stereo microscope, then the phase-polar examination, and finally the central stop dispersion microscopy.
Seattle Asbestos Test is equipped with a Phase-Polar Microscope with 10x 16x and 40x objectives, 10x wide-field eyepieces, G-22 Walton-Beckett reticule, Whipple disk, polarizer, analyzer and first order red or gypsum plate, 100 Watt illuminator, rotating position condenser with oversize phase rings, central stop dispersion objective, Kohler illumination and a rotating mechanical stage.