An Accessible Method for Screening Aerosol Filtration Identifies Poor-Performing Commercial Masks and Respirators

32 Pages Posted: 14 May 2020

See all articles by Katherine Schilling

Katherine Schilling

Department of Chemical & Environmental Engineering, Yale University

Drew Gentner

Department of Chemical & Environmental Engineering, Yale University

Lawrence Wilen

School of Engineering and Applied Science, Yale University

Antonio Medina

School of Engineering and Applied Science, Yale University

Colby Buehler

Department of Chemical & Environmental Engineering, Yale University

Luis J. Perez-Lorenzo

Department of Mechanical Engineering, Yale University

Krystal J. Godri Pollitt

Department of Chemical & Environmental Engineering, Yale University

Reza Bergemann

School of Engineering & Applied Science, Yale University

Nick Bernardo

School of Engineering & Applied Science, Yale University

Jordan Peccia

Department of Chemical & Environmental Engineering, Yale University

Vince Wilczynski

School of Engineering & Applied Science, Yale University

Lisa Lattanza

Department of Orthopaedics and Rehabilitation, Yale University

Date Written: April 28, 2020

Abstract

Background: The COVID-19 pandemic has presented an acute need for masks, specifically N95 respirators to be used by healthcare workers contacting COVID-19 patients and medical masks to be used by the public. The shortage of regulation NIOSH-tested masks make it necessary to find alternatives to protect frontline healthcare workers. Many of the available alternatives have not been NIOSH-certified or tested in the United States, leaving room for question as to whether they are performing at a level that is protecting the wearer from SARS-CoV-2 transmission. In addition, currently there are many counterfeit N95 and other masks being produced and sold as authentic products. It has become critical to be able to test these masks from non-traditional suppliers as well as the many masks that are being donated to hospitals at this time in order to ensure the safety of healthcare workers.

Methods: For situations where regulatory methods are not accessible, we present an experimental setup and screening method to evaluate mask filtration and breathability quickly via a cost-effective approach that could be replicated in communities of need without the extensive research infrastructure necessary for regulation mask tests. The experimental approaches presented here examined both mask aerosol filtration performance and mask flow impedance to ensure breathability, and mask fit tests were conducted in tandem but are not the focus of this study.

Findings: Tests conducted of 28 non-regulation masks using this setup reveal that a number of commercially- available masks in hospital inventories perform similarly to N95 masks for aerosol filtration of 0.2 μm and above. There are also a range of masks with relatively-weaker filtration efficiencies. Yet, a subset of commercially-available masks have poor filtration performance relative to N95 or similar masks at typical breathing velocities. All masks functioned acceptably with regards to breathability (i.e. flow impedance) and impedance was not correlated with filtration efficiency.

Interpretation: With a small set of simplified tests, organizations with critical personal protective equipment (PPE) shortages and uncertainties about their mask/respirator inventories can quickly evaluate the efficacy of their masks relative to N95-regulation masks to make informed decisions about which PPE to use and future procurement. This is essential since the results of this study use an actual diverse inventory of masks/respirators from a hospital network and show significant variability in their performance for filtering airborne aerosols that could contain SARS-CoV-2 and a subset of masks that would not be acceptable for frontline workers.

Note: Funding: Yale University, U.S. EPA, NSF.

Conflict of Interest: D.R.G. has externally-funded projects on low-cost air quality monitoring technology (EPA, HKF Technology), which Yale has licensed to HKF Technology. The remaining authors declare no conflict of interest.

Keywords: COVID-19, Personal Protective Equipment, Respirators, Masks, Aerosol Filtration, N95, SARS-CoV-2

Suggested Citation

Schilling, Katherine and Gentner, Drew and Wilen, Lawrence and Medina, Antonio and Buehler, Colby and Perez-Lorenzo, Luis J. and Godri Pollitt, Krystal J. and Bergemann, Reza and Bernardo, Nick and Peccia, Jordan and Wilczynski, Vince and Lattanza, Lisa, An Accessible Method for Screening Aerosol Filtration Identifies Poor-Performing Commercial Masks and Respirators (April 28, 2020). Available at SSRN: https://ssrn.com/abstract=3592485 or http://dx.doi.org/10.2139/ssrn.3592485

Katherine Schilling

Department of Chemical & Environmental Engineering, Yale University ( email )

New Haven, CT
United States

Drew Gentner

Department of Chemical & Environmental Engineering, Yale University ( email )

New Haven, CT
United States

Lawrence Wilen (Contact Author)

School of Engineering and Applied Science, Yale University ( email )

15 Prospect St
New Haven, CT CT 06510
United States

Antonio Medina

School of Engineering and Applied Science, Yale University ( email )

493 College St
New Haven, CT CT 06520
United States

Colby Buehler

Department of Chemical & Environmental Engineering, Yale University ( email )

New Haven, CT
United States

Luis J. Perez-Lorenzo

Department of Mechanical Engineering, Yale University ( email )

New Haven, CT
United States

Krystal J. Godri Pollitt

Department of Chemical & Environmental Engineering, Yale University ( email )

New Haven, CT
United States

Reza Bergemann

School of Engineering & Applied Science, Yale University ( email )

New Haven, CT
United States

Nick Bernardo

School of Engineering & Applied Science, Yale University ( email )

New Haven, CT
United States

Jordan Peccia

Department of Chemical & Environmental Engineering, Yale University ( email )

New Haven, CT
United States

Vince Wilczynski

School of Engineering & Applied Science, Yale University ( email )

New Haven, CT
United States

Lisa Lattanza

Department of Orthopaedics and Rehabilitation, Yale University ( email )

New Haven, CT
United States

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