Fit test for filtering facepieces: search for a low-cost, quantitative method.
Myojo-T; Willeke-K; Chen-C
Am Ind Hyg Assoc J 1994 Sep; 55(9):797-805
A new method for measuring the integrity of the seal of high efficiency particulate air (HEPA) and nonHEPA respirators to the face was demonstrated. In order to measure this fit quantitatively, particle penetration through filter pieces was distinguished from the penetration due to leakage around the face seal. This was accomplished by relating measured penetration to ratio of flow (FR) through the filter to the flow through the leak. Good comparison between calculated and measured penetration values demonstrated that aerosol penetration through filter and leaks is a function of this ratio and that FR can be calculated as a measure of face seal fit from the experimentally obtained aerosol penetration value if the filter penetration value is known. Using this relationship, three measures of fit were calculated from measured aerosol penetration including: the ratio of aerosol penetration at high to low flow rate; the slope of aerosol penetration with respect to FR ratio; and the fit index (FI), calculated by subtracting the inverse of aerosol penetration at a high flow rate from the inverse of aerosol penetration at low flow rate. FI proved to be the most sensitive to FR. Comparing predicted and experimentally determined fit index values at different flow rates demonstrated good agreement. Tests conducted on a human subject during breath holding and normal breathing also showed that the test produced acceptable results under either condition. The authors concluded that this new fit test provides a way to test the ability of low efficiency filtering facepieces to seal with the face without requiring HEPA filter cartridges to distinguish face seal leakage from filter penetration.
NIOSH-Publication; NIOSH-Grant; Respirators; Air-filters; Respiratory-protection; Protective-equipment; Face-masks; Leak-prevention; Laboratory-testing
Environmental Health University of Cincinnati Dept of Environmental Health Cincinnati, Ohio 45267
American Industrial Hygiene Association Journal
University of Cincinnati, Cincinnati, Ohio