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Particle size-dependent leakage and losses of aerosols in respirators.
Holton PM; Tackett DL; Willeke K
Am Ind Hyg Assoc J 1987 Oct; 48(10):848-854
The mechanisms of particle size dependent aerosol leakage into respirators were investigated. Leakage into a negative pressure half mask respirator equipped with air purifying cartridges worn by a human subject was measured utilizing three aerosols, a fine aerosol consisting of a mixture of smoke from burning incense and nebulized corn-oil, limestone dust, and corn-oil. The aerosols contained particles with diameters of 0.07 to 4.4 microns. Leakage was evaluated by measuring particle concentrations inside and outside the mask by an electrostatic aerosol classifier, condensation nucleus counter, active scattering aerosol spectrometer, or aerodynamic particle sizer. Comparison leakage tests utilizing 0.57, 1.07, or 1.68 millimeter (mm) diameter holes located at different places in the respirator, slits 4 or 10mm long, and sample probes placed in different locations inside the respirator were conducted. Total and particle size dependent leakage were strongly affected by where the holes and sampling probes were located. Total leakage was greater when a hole was placed in the chin area than when it was located near the nose. The further the sampling probe was from the leak site and closer it was to the clean air supply, the smaller the amount of leakage that was measured. Leakage of aerosol particles having diameters of 0.2 to 1.0 microns was not significantly affected by hole size. Total leakage decreased as hole size decreased; however, a greater percentage of large particles entered the hole as the hole size was decreased. Leakage was greater through circular holes than through slits. Leakage was not affected by slit length. The authors conclude that the location of the leak and sampling probe can exert a significant effect on the amount of leakage measured in a respirator.
NIOSH-Publication; NIOSH-Grant; Aerosol-particles; Personal-protective-equipment; Respiratory-protection; Laboratory-testing; Laboratory-techniques; Equipment-reliability
Environmental Health University of Cincinnati Dept of Environmental Health Cincinnati, Ohio 45267
Issue of Publication
American Industrial Hygiene Association Journal
University of Cincinnati, Cincinnati, Ohio
Page last reviewed: September 22, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division