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The results of studies examining the effects of wet stripping agents on the performance of asbestos filters used in powered respirators were summarized. Filters made of pleated glass fiber paper (PGFP) or resin wool used in two types of powered respirators designed for use during wet stripping of asbestos were tested for deterioration in filtration efficiency after being used in the field. The filters were evaluated by measuring the extent of penetration of diethyl-hexyl-sebacate (DEHS) and sodium-chloride aerosols using a specially designed apparatus. A simulated wet stripping operation was performed by spraying stripping agents in a confined tiled shower area by persons wearing respirators containing two types of resin filters. Liquid was sprayed at a rate of 10 liters per hour for periods of 15 minutes to 2.5 hours (hr). Changes in filtration efficiency of the filters were assessed by measuring the extent of penetration of a standard sodium-chloride aerosol before and between successive exposures. To test for transient effects, a number of PGFP and resin wool filters were exposed to coarse and fine sprays of wetting agents or water or encapsulating agents for various periods of time in the laboratory. Filtration efficiency was assessed using DEHS and sodium-chloride as the test penetrants. Slurries prepared from 3 grams (g) ground plaster board, 2g kaoline, and up to 10 milliliters of stripping agent were applied to the surfaces of the filters. The effects on filtration efficiency were assessed by measuring the number of particles appearing downstream from the filters. No significant deterioration in efficiency was seen in any of the filters that had been used in the field or in the simulation experiment. None of the stripping agent preparations significantly affected filtration efficiency of the PGFP filters in the laboratory experiments. The resin wool filters were degraded after exposure to very fine sprays of wetting agents, but not by exposure to coarse sprays, water, or encapsulating agents. The filter degradation induced by the fine sprays was not reversible, but did not progress if exposure was discontinued. No particle penetration was seen in filters treated with the slurries. The authors conclude that these data indicate that wet stripping of asbestos can be performed in a way that does not compromise respiratory protection. Respirators containing PGFP filters can be used under all conditions. Resin wool filters can be used with sprayed water or encapsulants.
Annals of Occupational Hygiene, 40(5):539-553, 1996. (11 references)
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