Reprocessing of N95 masks: Experience from a resource-limited setting in India.

OBJECTIVES: Due to the surge in demand for N95 masks during the Covid-19 pandemic, and considering the situation in countries grappling with acute shortages of N95 masks, this study investigated the possibilities of decontamination and reuse of masks. METHODS: Three N95 masks of different makes (A, B and C) were subjected to six decontamination methods: ultraviolet (UV) irradiation, isopropyl alcohol (IPA) dip, plasma sterilization (Sterrad®), ethylene oxide (ETO, 3M®), dry heat sterilization, and moist heat sterilization (autoclaving). The integrity of the N95 masks was assessed by measuring their particle filtering efficiency at particle sizes ranging 0.3-0.5 microns. RESULTS: All the masks decontaminated with ETO and plasma sterilization retained over 95% particle filtering efficiency. Masks decontaminated using IPA dip and autoclaving showed a drop, and UV irradiation showed variations in particle size efficiency degradation after decontamination. CONCLUSIONS: Plasma sterilization is recommended for decontamination of N95 masks in low-resource settings. ETO is not recommended due to hazards associated with handling of ethylene oxide, although the filtering efficiency was retained. Since the UV irradiation method showed variations in results, evaluation of UV decontamination for N95 masks needs to be performed on a case-by-case basis.

Fate of respiratory droplets in tropical vs temperate environments and implications for SARS-CoV-2 transmission.

The new pandemic of SARS-CoV-2 has shown stark differences in number of affected patients between countries in the tropics and those with temperate environments. Though there have been many theories on reasons for these differences, we hypothesise that this could be due to differences in the fate of respiratory droplets in the two environments. A simple understanding of the mechanics of droplet size, dispersion and displacement could help infection control and public health measures to minimize spread and mitigate the risk of people getting infected especially in hotspots like hospital environments or other closed spaces. This paper discusses the possibility of differences in number of infections and spread between different countries based on the spread of droplets.