Asbestos Fiber Collection by NIOSH (National Institute for Occupational Safety and Health): Approved Respirators. Final Performance Report

摘要

The first phase of the project involved assessing the size specific collection efficiencies of ten manufacturer's dust/mist respirator filters using monodisperse latex spheres. The second phase involved the evaluation of the overall collection efficiencies of three manufacturer's respirators using silica (14808607) and asbestos (1332214) aerosols under steady and cyclic flow conditions. The final phase involved an examination of the relationship between these empirical results and the predictions of both physically-based and semi-empirical models. Using latex spheres a high degree of efficiency, typically greater than 99.5%, was demonstrated by the dust/mist respirator filters for collecting particles with aerodynamic diameters greater than 1 micrometer. A minimum collection efficiency was noted of about 90% for particles with aerodynamic diameters of 0.1 micrometers. When the dust/mist respirators were challenged with a silica test aerosol, the overall mass collection efficiencies centered on 99.5% at steady flow conditions. Under cyclic flow conditions the silica penetration was about 50% greater than under steady flow. The authors recommended that The National Institute for Occupational Safety and Health (NIOSH) test its respirators as much as possible under conditions similar to those in actual use at the job site.