An accessible method for screening aerosol filtration identifies poor-performing commercial masks and respirators

• Published in: Journal of exposure science & environmental epidemiology Vol. 31; no. 6; pp. 943 - 952
• Main Authors: Schilling, Katherine, Gentner, Drew R., Wilen, Lawrence, Medina, Antonio, Buehler, Colby, Perez-Lorenzo, Luis J., Pollitt, Krystal J. Godri, Bergemann, Reza, Bernardo, Nick, Peccia, Jordan, Wilczynski, Vincent, Lattanza, Lisa
• Format: Journal Article
• Language: English
• Published: New York Nature Publishing Group US 01.11.2021; Nature Publishing Group
• Subjects: Accessibility; Aerosols; Control; COVID-19; Epidemics; Epidemiology; Experimental methods; Filtration; Humans; Impedance; Inventories; Masks; Medical personnel; Medicine; Medicine & Public Health; Pandemics; Respirators; Respiratory Protective Devices; SARS-CoV-2; Severe acute respiratory syndrome coronavirus 2; Shortages; United States; Ventilators, Mechanical; United States; COVID-19; SARS-CoV-2; Personal protective equipment (PPE); Masks; N95 respirators
• ISSN: 1559-0631; 1559-064X
• DOI: 10.1038/s41370-020-0258-7

Background The COVID-19 pandemic has presented an acute shortage of regulation-tested masks. Many of the alternatives available to hospitals have not been certified, leaving uncertainty about their ability to properly protect healthcare workers from SARS-CoV-2 transmission. Objective For situations where regulatory methods are not accessible, we present experimental methods to evaluate mask filtration and breathability quickly via cost-effective approaches (e.g., ~$2000 USD) that could be replicated in communities of need without extensive infrastructure. We demonstrate the need for screening by evaluating an existing diverse inventory of masks/respirators from a local hospital. Methods Two experimental approaches are presented to examine both aerosol filtration and flow impedance (i.e., breathability). For one of the approaches (“quick assessment”), screening for appropriate filtration could be performed under 10 min per mask, on average. Mask fit tests were conducted in tandem but are not the focus of this study. Results Tests conducted of 47 nonregulation masks reveal variable performance. A number of commercially available masks in hospital inventories perform similarly to N95 masks for aerosol filtration of 0.2 μm and above, but there is a range of masks with relatively lower filtration efficiencies (e.g., <90%) and a subset with poorer filtration (e.g., <70%). All masks functioned acceptably for breathability, and impedance was not correlated with filtration efficiency. Significance With simplified tests, organizations with mask/respirator shortages and uncertain inventories can make informed decisions about use and procurement.