Evaluation of filtration effectiveness of various types of facemasks following with different sterilization methods

Due to the ongoing pandemic, various types of facemasks such as certified N-95, non-woven fiber and fabric/textile masks are being used as an essential protective measure to reduce the risk of spread of the SARS-Cov-2 virus. The aerosols size-dependent filtration efficiency and breathing resistance of these masks were tested before and after sterilization by five different methods for two flow rates (20 and 90 L/min) conditions corresponding to regular breathing rate and moderate/strenuous exertion, in the particle size range 0.3–10 µm. Sterilization techniques used here are autoclaving (30 and 60 minutes), dry air oven heating (30 and 60 minutes), ionizing irradiation (15 and 25 kGy), hot water washing with and without detergent and immersing in a 10% concentration of liquid hydrogen peroxide for 30 minutes. Further, the filtration efficiency of each type of masks is also studied with laboratory generated two-order higher aerosol concertation. The certified mask has the most outstanding filtering efficiency among all the other type of facemasks. The ionizing radiation causes a significant reduction in filtration efficacy, so that it is not recommended for sterilization purpose. The best method to sterilize certified N-95 masks without affecting their performance is by using dry air heating with temperature ranging from 70–80 °C. The performance of the cloth and surgical masks is found to be comparable for both flow conditions. As an affordable sterilization method, hot water washing is recommended, which does not deteriorate the fabric masks efficiency and can be used by the common people. The recommended masks for the general people are textile/fabric masks which serves fit for the purpose than non-woven masks because it can help to reduce non-biodegradable waste (facemask) and prevent respiratory droplet transmission. The non-woven mask can be sterilized with dry heat, hot water wash and autoclave.