mendation should be modified to record separately the total number of fibers longer than 5, 10, and 20 µm. The subcommittee makes the same recommendation for determining concentrations of special-purpose MVF, which have a large fraction of fibers less than 1 µm in diameter.

For maintenance and removal operations where occupational exposures are likely to include high dust concentrations instead of or in addition to high fiber number concentrations, samplers with inlets that meet the ACGIH-ISO-CEN (American Conference of Governmental Industrial Hygienists-International Standards Organization-Comité Europeen de Normalisation) criteria for inhalable particulate matter should be used, and gravimetric determinations of the dust should be made.

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