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
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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.
