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Journal of Environmental and Public Health
Volume 2011, Article ID 402148, 9 pages
http://dx.doi.org/10.1155/2011/402148
Research Article

Using CO2 to Determine Inhaled Contaminant Volumes and Blower Effectiveness in Several Types of Respirators

1Fischell Department of Bioengineering, University of Maryland, College Park, MD 20742, USA
2National Personal Protection Technologies Laboratory, National Institute for Occupational Safety and Health, Pittsburgh, PA, USA

Received 16 September 2010; Revised 29 March 2011; Accepted 15 May 2011

Academic Editor: H. R. Guo

Copyright © 2011 Arthur T. Johnson et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

This experiment was conducted to determine how much contaminant could be expected to be inhaled when overbreathing several different types of respirators. These included several tight-fitting and loose-fitting powered air-purifying respirators (PAPRs) and one air-purifying respirator (APR). CO2 was used as a tracer gas in the ambient air, and several loose-and tight-fitting respirators were tested on the head form of a breathing machine. CO2 concentration in the exhaled breath was monitored as well as CO2 concentration in the ambient air. This concentration ratio was able to give a measurement of protection factor, not for the respirator necessarily, but for the wearer. Flow rates in the filter/blower inlet and breathing machine outlet were also monitored, so blower effectiveness (defined as the blower contribution to inhaled air) could also be determined. Wearer protection factors were found to range from 1.1 for the Racal AirMate loose-fitting PAPR to infinity for the 3M Hood, 3M Breath-Easy PAPR, and SE 400 breath-responsive PAPR. Inhaled contaminant volumes depended on tidal volume but ranged from 2.02 L to 0 L for the same respirators, respectively. Blower effectiveness was about 1.0 for tight-fitting APRs, 0.18 for the Racal, and greater than 1.0 for two of the loose-fitting PAPRs. With blower effectiveness greater than 1.0, some blower flow during the exhalation phase contributes to the subsequent inhalation. Results from this experiment point to different ways to measure respirator efficacy.