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Want to disinfect and reuse your N95 face mask? Autoclaving, alcohol may not be your best options

There is an acute shortage of N95 masks thanks to the demand in light of the COVID-19 pandemic.

According to a new study, common disinfection methods like autoclaving and alcohol may damage N95 face masks and make them ineffective.

Written by Jahnavi Sarma |Published : July 14, 2020 1:33 PM IST

The COVID-19 pandemic is raging on unabated and this has led to an acute shortage of personal protection equipment. Authorities now allow the reuse of face masks after sterilization in view of this scarcity. The Centers for Disease Control and Prevention (CDC) has also allowed the reuse of N95 respirators in a crisis situation. But you have to sterilise your face mask correctly for it to retain its effectiveness. A new study from the University of Cincinnati is advising against using two widely available sterilization methods to clean disposable surgical masks and N95 respirators for reuse in the midst of the coronavirus pandemic. The Journal of Hospital Infection published this study.

Researchers tested two brands of N95 respirators along with two types of surgical masks, one with high filtration and one with low-filtration abilities. For this purpose, they used an autoclave, which is an apparatus that works is a similar manner to a pressure cooker, to sterilize the face masks by using steam, heat and pressure during a specific time frame. They wanted to figure out what will happen with the performance of these N95 respirators and the surgical masks after they have spent minutes or longer in the autoclave and to what extent will the heat or steam destroy the structure of the filter making the items less useful.

Researchers also used another decontamination method which employed soaking the respirators and surgical masks in a 70 per cent ethanol treatment for two hours and then drying the devices before their reuse. Alcohol is readily available in hospital settings and utilized for instrument sterilization. Tests were conducted with disinfection treatments applied up to five times to simulate reusage that might occur in a healthcare setting.

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Effectiveness of masks deteriorated after first test

When multiple sterilizations were applied, face pieces were soiled before each autoclave treatment to mimic the device usage in air environments contaminated with protein that may be associated with emission of pathogenic virus by infected persons. Researchers chose to perform five soil and sterilization cycles to simulate a daily reuse of the filtering face mask over a period of five days.

According to researchers, it almost didn't matter how often they decontaminated the protective devices, once, twice or five times, since the major damage inflicted on the face masks happened after the first test itself. They saw that the performance of the masks fell if either of these treatments were used for sterilisaion. But they added that, quantitatively, the effect differs for different devices.

Treatments destroyed the electrostatic charge of masks

The 3M 8210 N95 respirator revealed physical damages after implementing a single autoclave disinfection such as partial disintegration of the soft sealing material around the nose clip, and, importantly, loss of strap elasticity, which made this respiratory protective device not reusable. N95 respirators and some surgical masks rely on fibers that have an electrostatic charge which allows them to capture small particles and protect the wearer. Autoclaving and alcohol treatment weaken this electrostatic charge. This affect filter performance and these protective devices may not be able to capture aerosol participles, including coronaviruses, as efficiently anymore.

UV rays more effective, say experts

According to researchers, instead of using autoclaving or ethanol alcohol to disinfect face masks and N95 respirator facepieces, alternative options such as ultraviolet light may be explored. They say that UV-based and probably other techniques may be almost as efficient as autoclaving and ethanol treatment in inactivating pathogens but at the same time would not damage the fibers of protective detectives so that the particle collection efficiency will not suffer.

(With input from Agencies)

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