Filtering facepiece respirators with an exhalation valve: measurements of filtration efficiency to evaluate their potential for source control.

Source avec lien : U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, 2020-12.

Ce rapport technique résume les recherches entreprises par le National Personal Protective Technology Laboratory (NPPTL) afin de fournir des recommandations scientifiques améliorées sur l’utilisation de masques respiratoires filtrants avec une valve d’expiration. Ces résultats montrent que les masques filtrants avec valve d’expiration offrent une protection respiratoire à l’utilisateur et peuvent également réduire les émissions de particules à des niveaux similaires ou supérieurs à ceux des masques chirurgicaux, des masques de procédure ou des revêtements faciaux en tissu. Cette étude montre également que les modifications apportées à ces respirateurs peuvent réduire davantage les émissions de particules. Plus précisément, l’utilisation d’un tampon d’électrocardiogramme ou d’un ruban chirurgical fixé sur la valve depuis l’intérieur du masque filtrant peut permettre un contrôle à la source similaire à celui d’un masque sans valve d’expiration. Ces résultats ont des implications importantes pour les orientations en matière de contrôle à la source et d’atténuation.

This technical report summarizes research undertaken by the National Personal Protective Technology Laboratory (NPPTL) to provide improved science-based recommendations on the use of filtering facepiece respirators (FFRs) with an exhalation valve. FFR models with an exhalation valve 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. Therefore, the question has emerged about the effectiveness of using an FFR with an exhalation valve for source control—i.e., to filter respiratory secretions to prevent disease transmission to others—and whether 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 findings in this report are based on tests of 13 FFR models from 10 different manufacturers. These findings show that FFRs with an exhalation valve provide respiratory protection to the wearer and can also reduce particle emissions to levels similar to or better than those provided by surgical masks, procedure masks, or cloth face coverings. This study also shows that modifications to these respirators can further reduce particle emissions. Specifically, the use of an electrocardiogram pad or surgical tape secured over the valve from the inside of the FFR can provide source control similar to that of an FFR with no exhalation valve. These findings have important implications for guidance on source control and mitigation.

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