COVID-19 research briefs: Not all face coverings offer similar degrees of protection

Daily POEMs

Published: 2020-10-17 © 2020 John Wiley & Sons, Inc.

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Clinical question
How effective are the different types of face masks for preventing the spread of COVID-19?

Bottom line
Based on laser testing, N95 masks transmitted less than 0.1% of respiratory droplets of COVID-19. (LOE = 2c)

Fischer EP, Fischer MC, Grass D, Henrion I, Warren WS, Westman E. Low-cost measurement of facemask efficacy for filtering expelled droplets during speech. Sci Adv 2020;6(36):eabd3083.

Study design: Other

Funding source: Unknown/not stated

Setting: Other

Research Brief #57: Although face masks have become a foundation of public health measures to mitigate the spread of respiratory illnesses such as COVID-19, they have also become lightning rods for various political agendas. Some people have used "face coverings" (eg, bandanas, gaiters, etc.) as a more comfortable or fashionable alternative to face masks. Analogous to other studies we have reported on the spread of respiratory droplets, this study used laser technology to evaluate the effectiveness of 14 different face coverings. The researchers included commercial and homemade masks, various materials, various numbers of layers, bandanas, gaiters, and a simple swath of mask material. They also included an unmasked control individual. One operator wearing each type of facial garb spoke into the darkened laser chamber and the flow of respiratory droplets were recorded and analyzed. An additional 4 operators wore a selection of the face coverings. The authors are proud to point out that their main equipment cost about $200; owning a cellphone camera means you can cheaply replicate their work! The clear winner was the commercially made, fitted N95 masks that transmitted less than 0.1% of the droplets compared with no mask. The clear loser was the gaiter-type neck fleece that actually transmitted more droplets than no mask (110%)! Bandanas were only slightly better than nothing. Although the study does not assess real-world performance, we have other empiric data that show various degrees of protection from commercial and homemade masks.

Henry C. Barry, MD, MS
Michigan State University
East Lansing, MI

Copyright © 2020 John Wiley & Sons, Inc.