Note: Covid-19 particles are 0.1 microns (micrometers).
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Wearing a used mask could be worse than no mask amid COVID-19: study
December 16, 2020
A new three-layer surgical mask is 65 percent efficient in filtering particles in the air — but when used, that number drops to 25 percent, according to the study published Tuesday in the Physics of Fluids.
Researchers from the University of Massachusetts Lowell and California Baptist University say that masks slow down airflow, making people more susceptible to breathing in particles — and a dirty face mask can’t effectively filter out the tiniest of droplets.
“It is natural to think that wearing a mask, no matter new or old, should always be better than nothing,” said author Jinxiang Xi.
“Our results show that this belief is only true for particles larger than 5 micrometers, but not for fine particles smaller than 2.5 micrometers.”…
They found that wearing a mask “significantly slows down” airflow, reducing a mask’s efficacy and making a person more susceptible to inhaling aerosols into the nose — where SARS-CoV-2 likes to lurk.…
The pleats of a face mask also significantly affect airflow patterns and their efficacy changes with more use, the researchers found.
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