Industrial Hygiene Sampling and Analysis Procedures

This is not a research study but a Johns-Manville company document on measuring dust in workplace air; one section is dated February 10, 1969. The first method, adapted with modifications from 1942 conference proceedings, drew air through an impinger into liquid and counted particles of 10 microns or less, defined as less than three times as long as wide; results were in millions of particles per cubic foot of air, and a worked example gave 15.8. The second, a membrane filter method, was for asbestos fibers in asbestos textile and mixed dust operations. A personal sampler worn by the worker drew air through a filter; fibers were counted at 430 times magnification with phase contrast optics, recording total fibers and fibers 5 microns and longer. Here, a particle at least three times as long as wide counted as a fiber. A worked example gave 9.5 fibers per cc. The document stated a maximum allowable concentration of 12 fibers per cc for fibers 5 microns and longer counted this way. No workers were studied and no health outcomes were reported.

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From J-M's medical library

This copy comes from the Johns-Manville medical library. It was among the papers J-M kept in its medical library without an index entry.