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What are the fitted filtration efficiencies (FFEs) of consumer-grade masks, improvised face coverings, and modified procedure masks commonly used during the coronavirus disease 2019 (COVID-19) pandemic?
In this comparative study of face covering FFEs, we observed that consumer-grade masks and improvised face coverings varied widely, ranging from 26.5% to 79.0% FFE. Modifications intended to enhance the fit of medical procedure masks improved FFE measurements from 38.5% (unmodified mask) to as much as 80.2%.
Simple modifications can improve the fit and filtration efficiency of medical procedure masks; however, the practical effectiveness of consumer-grade masks available to the public is, in many cases, comparable with or better than their non-N95 respirator medical mask counterparts.
During the coronavirus disease 2019 (COVID-19) pandemic, the general public has been advised to wear masks or improvised face coverings to limit transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, there has been considerable confusion and disagreement regarding the degree to which masks protect the wearer from airborne particles.
To evaluate the fitted filtration efficiency (FFE) of various consumer-grade and improvised face masks, as well as several popular modifications of medical procedure masks that are intended to improve mask fit or comfort.
Design, Setting, and Participants
For this study conducted in a research laboratory between June and August 2020, 7 consumer-grade masks and 5 medical procedure mask modifications were fitted on an adult male volunteer, and FFE measurements were collected during a series of repeated movements of the torso, head, and facial muscles as outlined by the US Occupational Safety and Health Administration Quantitative Fit Testing Protocol. The consumer-grade masks tested included (1) a 2-layer nylon mask with ear loops that was tested with an optional aluminum nose bridge and filter insert in place, (2) a cotton bandana folded diagonally once (ie, “bandit” style) or in a (3) multilayer rectangle according to the instructions presented by the US Surgeon General, (4) a single-layer polyester/nylon mask with ties, (5) a polypropylene mask with fixed ear loops, (6) a single-layer polyester gaiter/neck cover balaclava bandana, and (7) a 3-layer cotton mask with ear loops. Medical procedure mask modifications included (1) tying the mask’s ear loops and tucking in the side pleats, (2) fastening ear loops behind the head with 3-dimensional–printed ear guards, (3) fastening ear loops behind the head with a claw-type hair clip, (4) enhancing the mask/face seal with rubber bands over the mask, and (5) enhancing the mask/face seal with a band of nylon hosiery over the fitted mask.
Main Outcomes and Measures
The primary study outcome was the measured FFE of common consumer-grade and improvised face masks, as well as several popular modifications of medical procedure masks.
The mean (SD) FFE of consumer grade masks tested on 1 adult male with no beard ranged from 79.0% (4.3%) to 26.5% (10.5%), with the 2-layer nylon mask having the highest FFE. Unmodified medical procedure masks with ear loops had a mean (SD) FFE of 38.5% (11.2%). All modifications evaluated in this study increased procedure mask FFE (range [SD], 60.3% [11.1%] to 80.2% [3.1%]), with a nylon hosiery sleeve placed over the procedure mask producing the greatest improvement.
Conclusions and Relevance
While modifications to improve medical procedure mask fit can enhance the filtering capability and reduce inhalation of airborne particles, this study demonstrates that the FFEs of consumer-grade masks available to the public are, in many cases, nearly equivalent to or better than their non-N95 respirator medical mask counterparts.
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CME Disclosure Statement: Unless noted, all individuals in control of content reported no relevant financial relationships. If applicable, all relevant financial relationships have been mitigated.
Accepted for Publication: November 16, 2020.
Published Online: December 10, 2020. doi:10.1001/jamainternmed.2020.8168
Corresponding Author: Phillip W. Clapp, PhD, Department of Pediatrics, University of North Carolina at Chapel Hill, U.S. EPA Human Studies Facility, 104 Mason Farm Rd, Campus Box # 7310, Chapel Hill, NC 27599 (email@example.com).
Correction: This article was corrected on January 25, 2021, to fix an error in a recordered temperature and the use of the word “woven.”
Author Contributions: Drs Clapp and Bennett had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. Drs Clapp, Sickbert-Bennett, and Samet served as co–first authors and contributed equally to the work.
Concept and design: Clapp, Sickbert-Bennett, Samet, Weber, Bennett.
Acquisition, analysis, or interpretation of data: Clapp, Samet, Berntsen, Zeman, Anderson, Weber, Bennett.
Drafting of the manuscript: Clapp, Sickbert-Bennett, Weber, Bennett.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Clapp.
Obtained funding: Clapp, Sickbert-Bennett, Anderson, Weber.
Administrative, technical, or material support: Sickbert-Bennett, Samet, Berntsen, Weber, Bennett.
Supervision: Weber, Bennett.
Conflict of Interest Disclosures: Dr Clapp reported grants from the US Centers for Disease Control and Prevention (CDC) and UNC/US Environmental Protection Agency (EPA) Cooperative Agreement during the conduct of the study. Dr Sickbert-Bennett reported grants from CDC Epicenter (U54CK000483) during the conduct of the study. Dr Anderson reported grants from CDC Epicenter (U54CK000483) during the conduct of the study; grants from Agency for Healthcare Research and Quality, personal fees from UpToDate, and royalties for authorship outside the submitted work; and being the owner of Infection Control Education for Major Sports, LLC. Dr Weber reported grants from CDC during the conduct of the study. Dr Bennett reported grants from CDC during the conduct of the study and grants from the National Institutes of Health, US Department of Defense, US Food and Drug Administration, Cystic Fibrosis Foundation, and EPA outside the submitted work. No other disclosures were reported.
Funding/Support: This study was supported by the Duke-UNC Prevention Epicenter Program for Prevention of Healthcare-Associated Infections (U54CK000483) and a cooperative agreement between the University of North Carolina at Chapel Hill and the US Environmental Protection Agency (CR 83578501).
Role of the Funder/Sponsor: The funding organizations had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
CDC Epicenters Program Members: Phillip W. Clapp, PhD, University of North Carolina at Chapel Hill, Emily E. Sickbert-Bennett, PhD, MS, University of North Carolina Health Care, Deverick J. Anderson, MD, MPH, Duke University, David J. Weber, MD, MPH, University of North Carolina Health Care, and William D. Bennett, PhD, University of North Carolina at Chapel Hill.
Disclaimer: The research described in this article has been reviewed by the Center for Environmental Public Health and Environmental Assessment, EPA, and approved for publication. The contents of this article should not be construed to represent agency policy nor does mention of trade names or commercial products constitute endorsement or recommendation for use.
Additional Contributions: We thank Dr Bennett, the pictured author, for granting permission to publish this information.
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