Covid-19: Heat and humidity can help disinfect N95 masks for reuses, says study

A combination of heat and humidity can help disinfect N95 masks for reuse, according to a recent study.

Researchers at the Department of Energy's SLAC National Accelerator Laboratory, Stanford University and the University of Texas Medical Branch are studying a way to use a combination of moderate heat and high relative humidity to disinfect N95 mask materials without affecting their ability to filter out viruses.

Owing to the shortage of these masks, researchers have been trying to find a way to resume them including disinfecting the masks using ultraviolet light, hydrogen peroxide vapours, autoclaves and chemical disinfectants.

“The problem is that many of those methods degrade N95 masks' filtering abilities so that at most they could be reused a few times,” the report said.

As per the new study, heat and humidity may just do the trick.

Methodology

Researchers first created a fluid that can mimic the SARS-CoV-2 virus in fluids sprayed when we cough, sneeze, sing or breathe. They next sprayed droplets of this liquid on a piece of melt-blown fabric, a material used in most N95 masks, and let it dry.

After this, they heated their samples “at temperatures ranging from 25 to 95 degrees Celsius for up to 30 minutes with relative humidity up to 100 per cent.”

“Higher humidity and heat substantially reduced the amount of virus the team could detect on the mask, although they had to be careful not to go too hot, which additional tests revealed could lower the material's ability to filter out virus-carrying droplets. The sweet spot appeared to be 85 degrees Celsius with 100 per cent relative humidity - the team could find no trace of SARS-CoV-2 after cooking the masks under those conditions,” the report said.

“Masks could be decontaminated and reused upwards of 20 times and that the process works on at least two other viruses - a human coronavirus that causes the common cold and the chikungunya virus,” it added.

This method can be automated and used at hospitals to tackle the shortage of masks. It can also have a positive economic and climactic impact with less amount of waste is generated when masks can be reused.

"This is really an issue, so if you can find a way to recycle the masks a few dozen times, the shortage goes way down," said Stanford physicist Steven Chu, a senior author on the new paper. "You can imagine each doctor or nurse having their own personal collection of up to a dozen masks. The ability to decontaminate several of these masks while they are having a coffee break will lessen the chance that masks contaminated with Covid viruses would expose other patients."

The results are published in the journal ACS Nano .

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