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Challenge of N95 Filtering Facepiece Respirators with Viable H1N1 Influenza Aerosols

Published online by Cambridge University Press:  02 January 2015

Delbert A. Harnish ,
Brian K. Heimbuch ,
Michael Husband ,
April E. Lumley ,
Kimberly Kinney ,
Ronald E. Shaffer  and
Joseph D. Wander
Delbert A. Harnish*
Affiliation:
Applied Research Associates, Panama City, Florida
Brian K. Heimbuch
Affiliation:
Applied Research Associates, Panama City, Florida
Michael Husband
Affiliation:
Office of the Secretary, Assistant Secretary for Preparedness and Response, Biomedical Advanced Research and Development Authority, US Department of Health and Human Services, Washington, DC
April E. Lumley
Affiliation:
Applied Research Associates, Panama City, Florida
Kimberly Kinney
Affiliation:
Applied Research Associates, Panama City, Florida
Ronald E. Shaffer
Affiliation:
National Institute for Occupational Safety and Health, Pittsburgh, Pennsylvania
Joseph D. Wander
Affiliation:
Air Force Research Laboratory, Tyndall Air Force Base, Florida
*
Applied Research Associates, 430 West 5th Street, Suite 700, Panama City, FL 32401 (dharnish@ara.com)
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Abstract

Objective.

Specification of appropriate personal protective equipment for respiratory protection against influenza is somewhat controversial. In a clinical environment, N95 filtering facepiece respirators (FFRs) are often recommended for respiratory protection against infectious aerosols. This study evaluates the ability of N95 FFRs to capture viable H1N1 influenza aerosols.

Methods.

Five N95 FFR models were challenged with aerosolized viable H1N1 influenza and inert polystyrene latex particles at continuous flow rates of 85 and 170 liters per minute. Virus was assayed using Madin-Darby canine kidney cells to determine the median tissue culture infective dose (TCID50). Aerosols were generated using a Collison nebulizer containing H1N1 influenza virus at 1 × 108 TCID50/mL. To determine filtration efficiency, viable sampling was performed upstream and downstream of the FFR.

Results.

N95 FFRs filtered 0.8-μm particles of both H1N1 influenza and inert origins with more than 95% efficiency. With the exception of 1 model, no statistically significant difference in filtration performance was observed between influenza and inert particles of similar size. Although statistically significant differences were observed for 2 models when comparing the 2 flow rates, the differences have no significance to protection.

Conclusions.

This study empirically demonstrates that a National Institute for Occupational Safety and Health-approved N95 FFR captures viable H1N1 influenza aerosols as well as or better than its N95 rating, suggesting that a properly fitted FFR reduces inhalation exposure to airborne influenza virus. This study also provides evidence that filtration efficiency is based primarily on particle size rather than the nature of the particle's origin.

Type
Original Article
Information
Infection Control & Hospital Epidemiology , Volume 34 , Issue 5: Special Topic Issue: The Role of the Environment in Infection Prevention , May 2013 , pp. 494 - 499
Copyright
Copyright © The Society for Healthcare Epidemiology of America 2013

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