Evaluation of Cloth Masks and Modified Procedure Masks as Personal Protective Equipment for the Public During the COVID-19 Pandemic

Abstract

Importance: 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 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.

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 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.

Figure 1.. Consumer-Grade Masks and Improvised Face Coverings

The face coverings tested in this study included a 2-layer nylon mask with ear loops (54% recycled nylon, 43% nylon, 3% spandex), tested with and without an optional aluminum nose bridge and filter insert in place (A), a cotton bandana folded diagonally once “bandit” style (B), a cotton bandana folded in a multilayer rectangle according to the instructions presented by the US Surgeon General (C), a single-layer polyester/nylon mask (80% polyester, 17% nylon, 3% spandex) with ties (D), a polypropylene mask with fixed ear loops (E), a single-layer gaiter/neck cover balaclava bandana (92% polyester and 8% spandex) (F), and a 3-layer cotton mask (100% cotton) with ear loops (G).

Figure 2.. Medical Procedure Mask and Modifications Designed to Enhance Mask Fit or Comfort for the Wearer

A medical procedure mask with ear loops (A) was modified by tying the ear loops and tucking in the side pleats (B), attaching ear loops to a 3-dimensional–printed “ear guard” (C), fastening ear loops with a 23-mm claw-type hair clip placed behind the wearer’s head (D), placing a ring of 3 ganged rubber bands over the mask and around the wearer’s ears (E), and sliding a 10-inch segment of nylon hosiery over the fitted procedure mask (F).

Figure 3.. Evaluation of Fitted Filtration Efficiency (FFE) Using the US Occupational Safety and Health Administration Modified Ambient Aerosol CNC Quantitative Fit Testing Protocol for Filtering Facepiece

The overall FFE for a medical procedure mask with ear loops (A), medical procedure mask with the ear loops tied and mask corners tucked against the wearer’s face (B), and 2-layer nylon mask with an aluminum nose bridge and 1 filter insert (C) was 38.5%, 60.3%, and 74.4%, respectively. Particle penetration (y-axes) is defined as particle concentration behind the mask expressed as a percentage of the ambient particle concentration and is calculated during repeated-movement tests (bending at the waist, reading aloud, looking left and right, and looking up and down). The overall percentage of FFE is defined as 100 × (1 − behind the mask particle concentration / ambient particle concentration). Overall FFE percentage and SD were calculated across the length of the test. L/R indicates left/right; U/D, up/down.