Special Issue on COVID-19 Aerosol Drivers, Impacts and Mitigation (IV)

Eric P. Vejerano This email address is being protected from spambots. You need JavaScript enabled to view it., Jeonghyeon Ahn

Center for Environmental Nanoscience and Risk, Department of Environmental Health Sciences, Arnold School of Public Health, University of South Carolina, Columbia, South Carolina 29208, USA

Received: June 22, 2020
Revised: June 22, 2020
Accepted: June 29, 2020

 Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.

Download Citation: ||https://doi.org/10.4209/aaqr.2020.06.0339 

Cite this article:

Vejerano, E.P. and Ahn, J. (2020). A Letter to Reconsider the Conditions for Testing Decontaminated N95 Respirators for Emergency Reuse to Address Shortage. Aerosol Air Qual. Res. 20: 1713–1715. https://doi.org/10.4209/aaqr.2020.0.0339


  • N95 respirators tested at 85 L min–1 have predicted efficiencies of < 69%.
  • Experimental efficiencies of respirators tested at 85 L min–1 were < 55%.
  • Test flow rate should be closer to normal breathing.
  • Size of the test particle should reflect the size of respiratory aerosols.


The battle with COVID-19 pandemic has resulted in the shortage of personal protective equipment, particularly, N95 respirators. Healthcare workers who reused N95 respirators may resort to unproven methods of cleaning/sterilization that can severely compromise the respirators’ filtration efficiency. A recently issued guideline will test decontaminated N95 respirators against particles with a median diameter of 0.075 ± 0.020 µm at a flow rate of 85 L min–1. For emergency reuse, these conditions may be too stringent. N95 respirators tested at this flow rate had predicted efficiencies of < 69%, assuming complete degradation of their electrostatic coating. Experimental efficiencies were ~15% lower. For emergency reuse, we recommend to either adjust the flow rate closer to normal breathing, or the size of the test particle should reflect that of virus-laden respiratory aerosols (~> 0.5 µm). By reconsidering the test conditions, a substantial fraction of used/decontaminated respirators can be reused.

Aerosol Air Qual. Res. 20:1713-1715. https://doi.org/10.4209/aaqr.2020.06.0339 

Subscribe to our Newsletter 

Aerosol and Air Quality Research has published over 2,000 peer-reviewed articles. Enter your email address to receive latest updates and research articles to your inbox every second week.

Latest coronavirus research from Aerosol and Air Quality Research

2018 Impact Factor: 2.735

5-Year Impact Factor: 2.827

SCImago Journal & Country Rank

Sign up to AAQR Newsletter

Sign up to receive latest research, letters to the editors, and review articles, delivered to your inbox every second week!