Total outward leakage of half-mask respirators and surgical masks used for source control

Abstract

Both respirators and surgical masks (SM) are used as source control devices. During the COVID-19 pandemic, there was much interest in understanding the extent of particle total outward leakage (TOL) from these devices. The objective of this study was to quantify the TOL for five categories of devices: SMs, National Institute for Occupational Safety and Health (NIOSH) Approved N95 filtering facepiece respirators (FFRs) without exhalation valves, NIOSH Approved N95 FFRs with exhalation valves (N95 FFRV), NIOSH Approved elastomeric half-mask respirators (EHMRs) with exhalation valves, and NIOSH Approved EHMRs with an SM covering the exhalation valve (EHMRSM). A benchtop test system was designed to test two models of each device category. Each device was mounted on a headform at three faceseal levels (0% faceseal, 50% faceseal, and 100% faceseal). At each faceseal level, the TOL was assessed at three flow rates of minute ventilations of 17, 28, and 39 L/min. The experimental design was a split-split-plot configuration. Device type, faceseal level, flow rate, and the interaction of device type and faceseal level were found to have a significant effect ($p\text{-}\mathrm{value}$ < 0.05) on the TOL. This study found that the N95 FFRs without exhalation valves had the lowest mean TOL. The SMs had about three times higher TOL than the N95 FFRs without exhalation valves. The TOL of the N95 FFRV was comparable to that of the SM at 0% and 50% faceseal on average overall conditions, but the N95 FFRV had a significantly higher TOL than the SM at a 100% faceseal. The EHMRs had the highest TOL because of the exhalation valve. Using an SM to cover the exhalation valve did not improve the EHMRs’ efficiency in mitigating the TOL. Caution should be exercised when using N95 FFRVs as a source control measure against respiratory activities with heavy work rates, such as performing CPR. Results of this study showed that reduced faceseal leakage for N95 FFRs and SMs improves source control.

Keywords:

• COVID-19
• healthcare
• N95 filtering facepiece respirator
• respirator
• respiratory protection

Acknowledgments

The authors would like to thank National Personal Protective Technology Laboratory staff members Lee Portnoff, Lee Greenawald, and Kevin Strickland for their review of this paper. N95 and NIOSH Approved are certification marks of the U.S. Department of Health and Human Services (HHS) registered in the United States and several international jurisdictions. P100 is a certification mark of the U.S. Department of Health and Human Services (HHS) registered in the United States.

Data availability statement

The data will be available on the NIOSH Data and Statistics Gateway once cleared by NIOSH.

Disclaimer

The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention. Mention of any company or product does not constitute endorsement by the National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention.

Disclosure statement

The authors report this study has no conflicting interests to declare.

Additional information

Funding

This study was funded by the National Institute for Occupational Safety and Health (NIOSH), National Personal Protective Technology Laboratory (NPPTL) (Contract # 75D30120P09521).