Applying heat and humidity using stove boiled water for decontamination of N95 respirators in low resource settings

PLoS One. 2021 Sep 30;16(9):e0255338. doi: 10.1371/journal.pone.0255338. eCollection 2021.

Abstract

Global shortages of N95 respirators have led to an urgent need of N95 decontamination and reuse methods that are scientifically validated and available world-wide. Although several large scale decontamination methods have been proposed (hydrogen peroxide vapor, UV-C); many of them are not applicable in remote and low-resource settings. Heat with humidity has been demonstrated as a promising decontamination approach, but care must be taken when implementing this method at a grassroots level. Here we present a simple, scalable method to provide controlled humidity and temperature for individual N95 respirators which is easily applicable in low-resource settings. N95 respirators were subjected to moist heat (>50% relative humidity, 65-80°C temperature) for over 30 minutes by placing them in a sealed container immersed in water that had been brought to a rolling boil and removed from heat, and then allowing the containers to sit for over 45 minutes. Filtration efficiency of 0.3-4.99 μm incense particles remained above 97% after 5 treatment cycles across all particle size sub-ranges. This method was then repeated at a higher ambient temperature and humidity in Mumbai, using standard utensils commonly found in South Asia. Similar temperature and humidity profiles were achieved with no degradation in filtration efficiencies after 6 cycles. Higher temperatures (>70°C) and longer treatment times (>40 minutes) were obtained by insulating the outer vessel. We also showed that the same method can be applied for the decontamination of surgical masks. This simple yet reliable method can be performed even without electricity access using any heat source to boil water, from open-flame stoves to solar heating, and provides a low-cost route for N95 decontamination globally applicable in resource-constrained settings.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Asia / epidemiology
  • COVID-19 / epidemiology
  • COVID-19 / prevention & control*
  • COVID-19 / transmission
  • COVID-19 / virology
  • Decontamination / methods*
  • Equipment Reuse / statistics & numerical data*
  • Filtration
  • Hot Temperature*
  • Humans
  • Humidity*
  • Masks / standards*
  • N95 Respirators / standards*
  • SARS-CoV-2

Grants and funding

SD is supported by an Office of Technology and Licensing Stanford Graduate Fellowship. The Gordon and Betty Moore Foundation and Schmidt Foundation also supported MP in COVID related work. The National Science Foundation also supported this project through a grant given to MP (DBI-1548297). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.