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Cloth Masks and Modified Procedure Masks as PPE for the Public During the COVID-19 Pandemic
TAKE-HOME MESSAGE
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The authors evaluated the fitted filtration efficiency of consumer and improvised face masks used by the public during the COVID-19 pandemic. There was a wide range of fitted filtration efficiency seen in seven consumer-grade masks and five medical procedure mask modifications, with a two-layer woven nylon mask having the highest fitted filtration efficiency. Unmodified medical procedure masks with ear loops had a mean fitted filtration efficiency of 38.5%, with all investigated modifications giving improved filtration efficiency.
- Consumer-grade and improvised face masks in public use are nearly equivalent to or superior to medical procedure masks with regard to fitted filtration efficiency. The use of any of a wide range of options should be encouraged to reduce the spread of COVID-19 due to community transmission.
abstract
This abstract is available on the publisher's site.
Access this abstract nowImportance
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.
Objectives
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 woven nylon mask with ear loops that was tested with an optional aluminum nose bridge and nonwoven 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 woven polyester/nylon mask with ties, (5) a nonwoven polypropylene mask with fixed ear loops, (6) a single-layer woven polyester gaiter/neck cover balaclava bandana, and (7) a 3-layer woven 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.
Results
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 woven 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.
Additional Info
Disclosure statements are available on the authors' profiles:
Evaluation of Cloth Masks and Modified Procedure Masks as Personal Protective Equipment for the Public During the COVID-19 Pandemic
JAMA Intern Med 2020 Dec 10;[EPub Ahead of Print], PW Clapp, EE Sickbert-Bennett, JM Samet, J Berntsen, KL Zeman, DJ Anderson, DJ Weber, WD Bennett, US Centers for Disease Control and Prevention Epicenters ProgramFrom MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
A Potpourri of Masks
I used to think it curious—during those pre-pandemic travels to Asia—seeing people moving about their daily tasks while wearing facemasks. Now, I hardly give the potpourri of masks and face coverings that I encounter daily at the grocery, the hospital, or even on the street a second thought. They have become, at least in some locales, commonplace. We wear masks to protect our contacts—accidental, causal or otherwise--and we wear them to protect ourselves. The evidence has slowly and consistently and continuously mounted to the point where masking is an evidence-based norm of daily conduct in the pandemic. Given the plethora of styles, types, and patterns (to say nothing of the colors) one wonders if there are differentials in their effectiveness.
As it turns out, based on a small study from Clapp and colleagues, there definitely are differences.[1] The authors sought to evaluate a number of options, including simple bandanas (worn “bandit” style or folded and attached with rubber bands), cotton and nylon consumer-grade masks, and medical-grade procedure masks. They employed a custom-built exposure chamber filled with very small sodium chloride particles into which the test subject was placed. Using the Occupational Safety and Health Administration Fit Testing Protocol, fitted filter efficiency (FFE) was measured using a variety of masks and modifications. One should note that the “gold standard” here was our trusty N-95 respirator with an FFE of 98.4%.
Eighteen different masks or modifications are noted in this report. To provide a sampling, I present a selection from lowest (less effective) to highest (most effective) FFE:
With medical procedure masks (my usual go-to item), the gaps at the sides present a problem. This can be improved with easy rubber band fixes, or slipping a nylon hosiery band over your head, but at the cost of extreme loss of comfort.
I am now rethinking my supply of nice, stylish cotton masks with ear loops as well as my use of medical procedure masks. It may be time to invest in a good, washable, woven nylon mask with ear loops and a nose bridge.
References