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NIOSH), Centers for Disease Control and Prevention (CDC) Technical Report Filtering Facepiece Respirators with an Exhalation Valve: Measurements of Filtration Efficiency to Evaluate Their Potential for Source Control Centers for Disease Control and Prevention National Institute for Occupational Safety and Health Technical Report Filtering Facepiece Respirators with an Exhalation Valve: Measurements of Filtration Efficiency to Evaluate Their Potential for Source Control DEPARTMENT OF HEALTH AND HUMAN SERVICES Centers for Disease Control and Prevention National Institute for Occupational Safety and Health National Personal Protective Technology Laboratory This document is in the public domain and may be freely copied or reprinted. Disclaimer Mention of any company or product does not constitute endorsement by the National Institute for Occupational Safety and Health (NIOSH), Centers for Disease Control and Prevention (CDC). In addition, citations to websites external to NIOSH do not constitute NIOSH endorsement of the sponsoring organizations or their programs or products. Furthermore, NIOSH is not responsible for the content of these websites. All web addresses referenced in this document were accessible as of the publication date. Get More Information Find NIOSH products and get answers to workplace safety and health questions: 1-800-CDC-INFO (1-800-232-4636) | TTY: 1-888-232-6348 CDC/NIOSH INFO: cdc.gov/info | cdc.gov/niosh Monthly NIOSH eNews: cdc.gov/niosh/eNews Suggested Citation NIOSH [2020]. Filtering facepiece respirators with an exhalation valve: measurements of filtration efficiency to evaluate their potential for source control. By Portnoff L, Schall J, Brannen J, Suhon N, Strickland K, Meyers J. U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2021-107. https://doi.org/10.26616/NIOSHPUB2021107 DOI: https://doi.org/10.26616/NIOSHPUB2021107 DHHS (NIOSH) Publication No. 2021-107 December 2020 Cover photo by Shutterstock CONTENTS List of Figures ...............................................................................................................iv List of Tables .................................................................................................................iv Acronyms and Abbreviations ...................................................................................... v Unit of Measure Abbreviations .................................................................................... v Executive Summary ...................................................................................................... 1 Introduction ................................................................................................................... 3 Exhalation Valves ............................................................................................................ 4 Objective ......................................................................................................................... 5 Background ................................................................................................................... 5 Methods ......................................................................................................................... 6 Test Equipment ............................................................................................................... 7 Effect of Flowrate ............................................................................................................ 8 Control Group .................................................................................................................. 8 Inward Position......................................................................................................... 9 Outward Position ...................................................................................................... 9 Experimental Group ........................................................................................................ 9 Mitigation Strategies ................................................................................................. 9 Mitigation Strategy Selection .................................................................................. 10 Non-FFR Protective Devices ......................................................................................... 10 Filtration Test Findings ............................................................................................... 11 Discussion ................................................................................................................... 13 Limitations ..................................................................................................................... 15 Conclusions ................................................................................................................. 16 For Further Information ................................................................................................. 17 References ................................................................................................................... 18 Appendix ...................................................................................................................... 21 iii LIST OF FIGURES Figure 1. Simulations of particle exhalation through an FFR without an exhalation valve, an FFR with an exhalation valve, and a barrier face covering ............. 6 Figure 2. The two positions used for the 13 FFR models tested ..................................... 8 Figure 3. Three mitigations used on FFRs to measure the reduction of particle penetration .......................................................................................................... 9 Figure 4. Filtration efficiency by testing position at flowrates of 25, 55, and 85 lpm, reported as percentage of penetration .......................................................................... 11 Figure 5. Filtration efficiency of each FFR tested in the outward position control—i.e., with no mitigation measure ....................................................................... 12 Figure 6. Filtration efficiency of non-FFR protective devices by type, reported as percentage of penetration .......................................................................... 13 LIST OF TABLES Table 1. FFRs with an exhalation valve tested for this study ........................................... 7 Table A1. Particle penetration descriptive statistics by mitigation and flowrate among the 13 FFR models ............................................................................................ 21 Table A2. Particle penetration descriptive statistics by model for the outward and inward position controls ............................................................................ 22 Table A3. Particle penetration descriptive statistics by flowrate among each of the four non-FFR protective devices ..................................................... 23 iv ACRONYMS AND ABBREVIATIONS CDC Centers for Disease Control and Prevention CMD count median diameter FFR filtering facepiece respirator GSD geometric standard deviation HCP healthcare personnel MMAD mass median aerodynamic diameter NaCl sodium chloride NIOSH National Institute for Occupational Safety and Health NPPTL National Personal Protective Technology Laboratory PAPR powered air-purifying respirator UNIT OF MEASURE ABBREVIATIONS cm centimeter g gram g/cc grams per cubic centimeter in inches lpm liters per minute mg/m3 milligrams per cubic meter mm millimeter mmH2O millimeters of water column nm nanometer µm micrometer v EXECUTIVE SUMMARY Filtering facepiece respirators (FFRs) are used extensively by healthcare personnel (HCP) during a pandemic. FFRs are primarily reserved for those personnel who have a greater risk and longer duration of exposure compared with other workers and the general public. Some FFR models contain an exhalation valve, which is a device that closes to allow inhaled breath to be pulled through the filter media and opens in order to allow exhaled breath to be expelled from the respirator through the exhalation valve as well as the filter media. These FFR models provide the wearer with a level of protection similar to that of an FFR without an exhalation valve, and they are thought to increase the wearer’s comfort at high work rates and be suitable for longer periods of use. However, respiratory secretions expelled by wearers may exit along with air through the exhalation valve. A concern with FFRs with an exhalation valve is that individuals may spread disease if unfiltered, virus-laden aerosols pass through the valve. Current guidance from the Centers for Disease Control and Prevention (CDC) does not recommend using an FFR with an exhalation valve for source control (i.e., to filter respiratory secretions to prevent disease transmission to others) and advises that if only this option is available and source control is needed, then the valve should be covered with a surgical mask, procedure mask, or a cloth face covering that does not interfere with the respirator fit. The CDC has requested research in order to provide improved science-based recommendations on the use of exhalation valves. The current study was designed to respond to this request and to evaluate particle penetration in FFRs with an exhalation valve. Further, this research compares mitigation strategies, including investigating the practice of covering the FFR exhalation valve
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