Faced with shortages, researchers combine heat and humidity to disinfect
N95 masks

Date:
September 26, 2020
Source:
DOE/SLAC National Accelerator Laboratory
Summary:
Researchers found that gently heating N95 masks in high relative
humidity could inactivate SARS-CoV-2 virus trapped within the masks,
without degrading the masks' performance.



FULL STORY ==========================================================================
As the COVID-19 pandemic swept around the world early this year, shortages
of protective equipment such as N95 masks left healthcare workers little
choice but to reuse the masks they had -- increasing the risk of infection
for both them and their patients.


==========================================================================
Now, researchers at the Department of Energy's SLAC National Accelerator Laboratory, Stanford University and the University of Texas Medical
Branch may have a solution: Using a combination of moderate heat and
high relative humidity, the team was able to disinfect N95 mask materials without hampering their ability to filter out viruses.

What's more, it should not be too difficult to turn the new results
into an automated system hospitals could use in short order -- because
the process is so simple, it might take just a few months to design and
test a device.

"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 team reported their results September 25th in the journal ACS Nano.

Facing a shortage of the masks early this year, researchers considered a
number of ways to disinfect them for reuse, including ultraviolet light, hydrogen peroxide vapors, 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.



==========================================================================
In the new study, Chu, University of Texas Medical Branch virologist Scott Weaver and Stanford/SLAC professors Yi Cui and Wah Chiu and colleagues
focused their attention on a combination of heat and humidity to try to decontaminate masks.

Working at the World Reference Center for Emerging Viruses and
Arboviruses, which has biosafety measures in place for working with the
most contagious viruses, the team first mixed up batches of SARS-CoV-2
virus in liquids designed to mimic the fluids that might spray out of our mouths when we cough, sneeze, sing or simply breathe. They next sprayed droplets of the brew on a piece of meltblown fabric, a material used in
most N95 masks, and let it dry.

Finally, they heated their samples at temperatures ranging from 25 to
95 degrees Celsius for up to 30 minutes with relative humidity up to
100 percent.

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 percent relatively humidity -- the
team could find no trace of SARS- CoV-2 after cooking the masks under
those conditions.

Additional results indicate 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.

Weaver said that although the results are not especially surprising - - researchers have known for a long time that heat and humidity are good
ways to inactivate viruses -- there hadn't been an urgent need for a
detailed quantitative analysis of something like mask decontamination
until now. The new data, he said, "provide some quantitative guidance
for the future." And even after the coronavirus pandemic is over,
there are likely benefits, in part because of the method's application
beyond SARS-CoV-2 to other viruses, and because of the economic and environmental benefits of reusing masks. "It's good all around," Cui said.

The research was supported by the DOE Office of Science through the
National Virtual Biotechnology Laboratory, a consortium of DOE national laboratories focused on response to COVID-19, with funding provided by
the Coronavirus CARES Act and by World Reference Center for Emerging
Viruses and Arboviruses, funded by the National Institutes of Health.


========================================================================== Story Source: Materials provided by
DOE/SLAC_National_Accelerator_Laboratory. Original written by Nathan
Collins. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Rafael K Campos, Jing Jin, Grace H. Rafael, Mervin Zhao, Lei
Liao, Graham
Simmons, Steven Chu, Scott c Weaver, Wah Chiu, Yi
Cui. Decontamination of SARS-CoV-2 and Other RNA Viruses from N95
Level Meltblown Polypropylene Fabric Using Heat under Different
Humidities. ACS Nano, 2020; DOI: 10.1021/acsnano.0c06565 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200926145145.htm

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