Annals of Occupational Hygiene Advance Access published online on August 21, 2009
Annals of Occupational Hygiene, doi:10.1093/annhyg/mep062
Large Particle Penetration through N95 Respirator Filters and Facepiece Leaks with Cyclic Flow
1 Center for Health-Related Aerosol Studies, University of Cincinnati, Cincinnati, OH 45267, USA
2 Center for Biostatistical Services, University of Cincinnati, Cincinnati, OH 45267, USA
3 Koken Ltd., 7, Yonbancho, Chiyoda-ku, Tokyo 102-8459, Japan
* Author to whom correspondence should be addressed. Tel: +513-558-0571; fax: +513-558-2263; e-mail: tiina.reponen{at}uc.edu
The aim of this study was to investigate respirator filter and faceseal penetration of particles representing bacterial and fungal spore size ranges (0.7–4 µm). First, field experiments were conducted to determine workplace protection factors (WPFs) for a typical N95 filtering facepiece respirator (FFR). These data (average WPF = 515) were then used to position the FFR on a manikin to simulate realistic donning conditions for laboratory experiments. Filter penetration was also measured after the FFR was fully sealed on the manikin face. This value was deducted from the total penetration (obtained from tests with the partially sealed FFR) to determine the faceseal penetration. All manikin experiments were repeated using three sinusoidal breathing flow patterns corresponding to mean inspiratory flow rates of 15, 30, and 85 l min–1. The faceseal penetration varied from 0.1 to 1.1% and decreased with increasing particle size (P < 0.001) and breathing rate (P < 0.001). The fractions of aerosols penetrating through the faceseal leakage varied from 0.66 to 0.94. In conclusion, even for a well-fitting FFR respirator, most particle penetration occurs through faceseal leakage, which varies with breathing flow rate and particle size.
cyclic flow • faceseal • filter • penetration • protection factor • respirator
Received March 12, 2009; in final form July 24, 2009