Heating best method for disinfection of N95 masks, finds study
Researchers have revealed that heating was recently found to inactivate the coronavirus in solution within 5 min at 70 °C and is among the most scalable, user-friendly methods for viral disinfection of N 95 masks. Heating them preserves their filtration efficiency for 50 cycles of disinfection.The findings of the research have been reported in ACS Nano.
Scientists have been working on finding ways and means for disinfection of disposable N95 respirator masks amid shortages of personal protective equipment due to the Coronavirus Disease 2019 (COVID-19) pandemic.
A novel disinfection process appearing in Journal of the American College of Surgeons uses vaporized hydrogen peroxide for disinfection of disposable N95 respirator masks.
N95 masks contain a layer of "meltblown" polypropylene fibers that form a porous, breathable network. To help capture smaller particles that could slip through the holes, the fibers are electrostatically charged. The U.S. Centers for Disease Control and Prevention has recommended several methods for disinfecting N95 masks, such as heating, ultraviolet (UV) radiation and bleach treatment, but so far they have not been tested extensively, especially for multiple rounds of disinfection. Yi Cui and colleagues wanted to compare five of the methods that could reasonably be used within a hospital setting to see how mask materials hold up to repeated disinfections.
In this study, instead of analyzing N95 masks -- which should be reserved for health care workers -- the researchers examined pieces of the meltblown fabric used to make these masks. They treated the material with a particular disinfectant and compared its ability to filter aerosol particles (resembling respiratory droplets, but lacking coronavirus) before and after disinfection. The team found that spraying the fabric with an ethanol or chlorine bleach solution drastically reduced the filtration efficiency after only one treatment, from about 96% to 56% (ethanol) or 73% (bleach). A single steam treatment maintained filtration, but five steam treatments led to a sharp decline in efficiency. UV radiation allowed up to 20 cycles of disinfection; however, administering the exact dose of UV that kills the virus without damaging mask materials could be problematic, the researchers note. The best disinfection method appeared to be heating. For example, heating at 185 F for 20 minutes allowed the fabric to be treated 50 times without loss of filtration efficiency. But frequently donning and removing N95 masks could affect fit, which also impacts performance, the researchers point out.
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