Collection of silica and asbestos aerosols by respirators at steady and cyclic flow.
Brosseau-LM; Ellenbecker-MJ; Evans-JS
Am Ind Hyg Assoc J 1990 Aug; 51(8):420-426
The performance of electrostatically charged dust/mist respirator filters when challenged with silica (7631869) and asbestos (1332214) were studied under conditions similar to those used for NIOSH approval tests (continuous flow of 0.032 cubic meters/minute) and under conditions of cyclic flow. The filters were obtained from three different manufacturers. Under continuous flow conditions, the mass penetration of silica averaged 0.1% or less for filters from all three manufacturers. Mass penetration of silica at cyclic flow averaged 0.2% for manufacturer 1, 0.4% for manufacturer 2, and 1.1% for manufacturer 3. With asbestos, penetration under continuous flow conditions was almost always less than 0.5%. Under cyclic flow conditions, penetration of asbestos was less than 0.1% for filters from manufactures 1 and 2 and about 0.6% for manufacturer 3. The results suggest that respirator tests using silica aerosols may not be indicative of the performance that will be experienced when respirators are challenged with asbestos aerosols. Further, the study indicates that greater aerosol penetration occurs under conditions of cyclic flow than under steady flow. Finally, it appears that the stress on exhalation valves under cyclic flow may be sufficient to induce valve failure and thereby dramatically increase aerosol penetration into the respirator. In light of these findings the authors suggest that the NIOSH testing methods which rely on assessment of mass penetration of silica aerosols under steady flow conditions should be reconsidered. In addition they suggest that methods for evaluating the life cycle performance of respiratory components such as valves should be developed.
NIOSH-Publication; NIOSH-Grant; Respirators; Training; Equipment-reliability; Silica-dusts; Personal-protective-equipment; Respiratory-protective-equipment; Asbestos-fibers
Physiology Department, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115
American Industrial Hygiene Association Journal
Harvard University, Boston, Massachusetts