Nanoparticle Penetration through Filter Media and Leakage through Face Seal Interface of N95 Filtering Facepiece Respirators

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Samy Rengasamy1,* and Benjamin C. Eimer2

1Policy and Standard Development Branch, National Institute for Occupational Safety and Health, National Personal Protective Technology Laboratory, 626 Cochrans Mill Road, PO Box 18070, Pittsburgh, PA 15236, USA

2Policy and Standard Development Branch, URS, Corporation 626 Cochrans Mill Road, PO Box 18070, Pittsburgh, PA 15236, USA ?* Author to whom correspondence should be addressed. Tel: 1-412-386-6853; Fax: 1-412-386-4089; e-mail: ARengasamy{at}cdc.gov Received June 17, 2011. Accepted December 16, 2011. National Institute for Occupational Safety and Health recommends the use of particulate respirators for protection against nanoparticles (<100 data-blogger-escaped-20="20" data-blogger-escaped-400="400" data-blogger-escaped-45="45" data-blogger-escaped-50="50" data-blogger-escaped-8="8" data-blogger-escaped-a="a" data-blogger-escaped-afforded="afforded" data-blogger-escaped-all="all" data-blogger-escaped-although="although" data-blogger-escaped-and="and" data-blogger-escaped-any="any" data-blogger-escaped-artificially="artificially" data-blogger-escaped-as="as" data-blogger-escaped-at="at" data-blogger-escaped-been="been" data-blogger-escaped-better="better" data-blogger-escaped-breathing="breathing" data-blogger-escaped-by="by" data-blogger-escaped-combination="combination" data-blogger-escaped-component="component" data-blogger-escaped-concerning="concerning" data-blogger-escaped-condition="condition" data-blogger-escaped-considered="considered" data-blogger-escaped-documented="documented" data-blogger-escaped-efficiency="efficiency" data-blogger-escaped-expanded="expanded" data-blogger-escaped-extent="extent" data-blogger-escaped-face-to-facepiece="face-to-facepiece" data-blogger-escaped-face="face" data-blogger-escaped-facepiece="facepiece" data-blogger-escaped-filter="filter" data-blogger-escaped-filtering="filtering" data-blogger-escaped-for="for" data-blogger-escaped-four="four" data-blogger-escaped-function="function" data-blogger-escaped-have="have" data-blogger-escaped-higher="higher" data-blogger-escaped-i.e.="i.e." data-blogger-escaped-in="in" data-blogger-escaped-information="information" data-blogger-escaped-interfaces="interfaces" data-blogger-escaped-introduced="introduced" data-blogger-escaped-inward="inward" data-blogger-escaped-is="is" data-blogger-escaped-l="l" data-blogger-escaped-laboratory="laboratory" data-blogger-escaped-lacking.="lacking." data-blogger-escaped-leakage="leakage" data-blogger-escaped-leaks="leaks" data-blogger-escaped-manikin.="manikin." data-blogger-escaped-measure="measure" data-blogger-escaped-measured="measured" data-blogger-escaped-mechanisms="mechanisms" data-blogger-escaped-media="media" data-blogger-escaped-minute="minute" data-blogger-escaped-models.="models." data-blogger-escaped-models="models" data-blogger-escaped-most="most" data-blogger-escaped-mpps="mpps" data-blogger-escaped-n95="n95" data-blogger-escaped-nanoparticle="nanoparticle" data-blogger-escaped-nm="nm" data-blogger-escaped-of="of" data-blogger-escaped-our="our" data-blogger-escaped-particle="particle" data-blogger-escaped-particles.="particles." data-blogger-escaped-particles="particles" data-blogger-escaped-particulate="particulate" data-blogger-escaped-penetrating="penetrating" data-blogger-escaped-penetration="penetration" data-blogger-escaped-previous="previous" data-blogger-escaped-protection="protection" data-blogger-escaped-respirator="respirator" data-blogger-escaped-respirators="respirators" data-blogger-escaped-results="results" data-blogger-escaped-s="s" data-blogger-escaped-seal.="seal." data-blogger-escaped-seal="seal" data-blogger-escaped-sealed="sealed" data-blogger-escaped-showed="showed" data-blogger-escaped-significance="significance" data-blogger-escaped-significantly="significantly" data-blogger-escaped-size="size" data-blogger-escaped-specific="specific" data-blogger-escaped-study="study" data-blogger-escaped-than="than" data-blogger-escaped-that="that" data-blogger-escaped-the="the" data-blogger-escaped-this="this" data-blogger-escaped-through="through" data-blogger-escaped-til="til" data-blogger-escaped-to="to" data-blogger-escaped-total="total" data-blogger-escaped-understand="understand" data-blogger-escaped-using="using" data-blogger-escaped-volumes="volumes" data-blogger-escaped-was="was" data-blogger-escaped-well="well" data-blogger-escaped-with="with"> < 0.05) higher than the values for 400 nm size particles. A consistent increase in filter penetrations for 45 and 400 nm size particles was obtained with increasing breathing minute volumes. Artificial leakage of test aerosols (mode size ~75 nm) through increasing size holes near the sealing area of FFRs showed higher TIL values for 45 nm size particles at different minute volumes, indicating that the induced leakage allows the test aerosols, regardless of particle size, inside the FFR, while filter penetration determines the TIL for different size particles. TIL values obtained for 45 nm size particles were significantly (P

< 0.05) higher than the values obtained for 400 nm size particles for all four models. Models with relatively small filter penetration values showed lower TIL values than the models with higher filter penetrations at smaller leak sizes indicating the dependence of TIL values on filter penetration. When the electrostatic charge was removed, the FFRs showed a shift in the MPPS to ~150 nm with the same test aerosols (mode size ~75 nm) at different hole sizes and breathing minute volumes, confirming the interaction between filter penetration and face seal leakage processes. The shift in the MPPS from 45 to 150 nm for the charge removed filters indicates that mechanical filters may perform better against nanoparticles than electrostatic filters rated for the same filter efficiency. The results suggest that among the different size particles that enter inside the N95 respirators, relatively high concentration of the MPPS particles in the breathing zone of respirators can be expected in workplaces with high concentration of nanoparticles. Overall, the data obtained in the study suggest that good fitting respirators with lower filter penetration values would provide better protection against nanoparticles. Published by Oxford University Press on behalf of the British Occupational Hygiene Society 2012This ArticleAnn Occup Hyg (2012) 56 (5): 568-580. doi: 10.1093/annhyg/mer122 First published online: January 31, 2012 Current Issue
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