Applying Heat and Humidity using Stove Boiled Water for Decontamination of N95 Respirators in Low Resource Settings

Doshi, S., Banavar, S. P., Flaum, E., Kulkarni, S., Vaidya, U., Kumar, S., Chen, T., Bhattacharya, A., & Prakash, M. (2021). Applying heat and humidity using stove boiled water for decontamination of N95 respirators in low resource settings. Plos one, 16(9), e0255338.

Link: https://www.medrxiv.org/content/10.1101/2020.05.28.20113209v3

• 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 0.3-4.99um 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 temperatures and humidities were achieved and filtration efficiencies consistently remained above 94%. Higher temperatures (>70°C) and longer treatment times (>40 minutes) were obtained by insulating the outer vessel. 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.