Characteristics of face seal leakage in filtering facepieces.
Am Ind Hyg Assoc J 1992 Sep; 53(9):533-539
Characteristics of face seal leakage in filtering facepieces were examined, with emphasis on the effects of leak shape and filter resistance on the fit factor. Aerosol penetration was assessed using four leaks of different shape but the same cross sectional area. Dust mist (DM) and high efficiency particulate air (HEPA) filtering facepieces were chosen to provide different filter resistances at constant flow rates ranging from 5 to 100 liters per minute. An aerodynamic particle sizer and a laser aerosol spectrometer were used to measure particle size dependent aerosol concentrations inside and outside the respirators. Facepieces were sealed to mannequins; pressure drops across the masks were monitored with inclined manometers. Aerosol penetration decreased with increasing leak shape complexity. At any given pressure differential, slit like leaks and multiple circular leaks passed less aerosols than did single circular leaks of equal cross sectional area. The pressure drop was considerably higher for the HEPA respirator than for the DM respirator. The authors conclude that the HEPA respirator may provide less protection than the DM respirator if there is substantial lack of face seal fit and the workload is light; if the leak size is small, the HEPA respirator performs better.
NIOSH-Publication; NIOSH-Grant; Respirators; Face-masks; Air-filters; Respiratory-protective-equipment; Personal-protective-equipment; Respiratory-equipment; Equipment-design
Environmental Health University of Cincinnati Dept of Environmental Health Cincinnati, Ohio 45267
American Industrial Hygiene Association Journal
University of Cincinnati, Cincinnati, Ohio