Penetration of respirator filters by an asbestos aerosol.

Five models of respirator filters were challenged with a chrysotile aerosol, and the asbestos fiber penetration of the media was measured in five experimental series simulating different environmental conditions. Penetration of the facial seal was not evaluated. The penetration of each filter was determined from the ratio of the downstream to upstream concentrations of airborne asbestos fibers as measured by the standard National Institute for Occupational Safety and Health (NIOSH) asbestos fiber counting method P&CAM 239. Penetrations measured in this project and presented are indicative of penetrations of filters used a) fresh from the package, b) after exposure to an organic oil mist, c) after storage at high humidity at room and elevated temperatures, and d) after preexposure to water mist. Penetrations varied between less than 0.1% and 2.7% for filters tested fresh from the package and up to 18% after exposure to simulated field/environmental conditions. The data indicate that each of the filter models tested, except for the high efficiency filter, was affected adversely to some degree by one or more of the simulated field/environmental conditions.