Warming helps to disinfect N95 face masks safely
N95 face masks have become scarce in times of the COVID-19 pandemic, heating helps to disinfect the masks effectively, so they can be used safely several times. This could help prevent infections with the cornavirus, even if there is a shortage of mask.
The current investigation by Stanford University found that proper heating can ensure disinfection of N95 materials. The results of the study were published in the English language journal “ACS Nano”.
Warming enabled safe multiple use of the masks
Due to the lack of N95 face masks, healthcare workers in particular have to wear the same mask again and again. When investigating various methods for disinfecting N95 materials, it was found that their filtration efficiency is maintained when heated over 50 disinfection cycles.
How do N95 masks work?
N95 masks contain a layer of polypropylene fibers that form a porous, breathable network. The fibers are electrostatically charged to make it easier to collect smaller particles. Various methods such as heating, ultraviolet radiation and bleach treatment for disinfecting N95 masks have been recommended. However, these have not yet been extensively examined.
The fabric of N95 masks was examined closely
The researchers compared five methods that can be used in a hospital to determine how the mask materials withstand repeated disinfection. They did not use N95 masks for this, but pieces of the special fabric used to manufacture the masks were examined.
Material was treated with various disinfectants
The research group treated the material with a specific disinfectant and then compared its ability to filter aerosol particles (which resemble respiratory droplets but do not contain a coronavirus) before and after disinfection. The team found that spraying the fabric with an ethanol or chlorine bleach solution drastically reduced filtration efficiency after just one treatment.
Ethanol and bleach drastically reduced filtration efficiency
When disinfected with ethanol, the filtration efficiency was reduced from around 96 percent to 56 percent. Bleach, on the other hand, reduced the filtration efficiency to 73 percent. A single steam treatment maintained the filtration, but five steam treatments resulted in a sharp drop in efficiency.
What did ultraviolet radiation do?
UV radiation allowed up to 20 disinfection cycles. However, according to the researchers, the use can be problematic because the exact UV dose is difficult to determine. Too little radiation does not kill the virus sufficiently – too much radiation damages the material of the mask.
Optimal method for disinfecting N95 masks?
The best disinfection method seemed to be warming. For example, heating for 20 minutes at 185 degrees Fahrenheit (85 degrees Celsius) allowed the fabric to be treated 50 times without loss of filtration efficiency. However, the frequent putting on and taking off of N95 masks could impair the fit, which also affects performance, the researchers report. (as)
Sources:
- Lei Liao, Wang Xiao, Mervin Zhao, Xuanze Yu, Haotian Wang et al .: Can N95 Respirators Be Reused after Disinfection? How Many Times ?, in ACS Nano (Published May 5, 2020), ACS Nano
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Important NOTE:
This article contains general information only and should not be used for self-diagnosis or treatment. He can not substitute a visit at the doctor.
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