The Industrial Environment: its Evaluation and Control (Syllabus) (1970)

This is not a research study. It is a chapter titled "Dust Counting Techniques" from a U.S. Public Health Service training syllabus, "The Industrial Environment: Its Evaluation and Control" (first printed 1958, revised 1965, reprinted 1970). It described the standard method, presented in 1942, for sampling workplace air with impingers and counting dust particles under a light microscope, with results given in millions of particles per cubic foot of air. The chapter did not mention asbestos. In one project it described, about 100 samples were counted in the field within 24 hours and counted again 1 to 2 weeks later. Only 25% of the pairs fell within the 50% limits and 55% within the 90% limits, and 65% gave lower counts in the laboratory. Calculated settling times were about 25 minutes per millimeter for 1 micron quartz particles in water and about 33 in ethyl alcohol. Alcohol-water mixtures, lighter dusts such as coal, and observer eyesight could change counts. The chapter suggested counting about 400 particles per sample as a reasonable minimum and choosing settling times so counts match those for quartz in water.

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From J-M's medical library

This copy comes from the Johns-Manville medical library. It is a copy from J-M's medical library.