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Study: N95 masks without valves most effective against COVID-19

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N95 masks without valves are most effective at protecting against the new coronavirus, followed by surgical or polypropylene masks, researchers say. Photo by RevsReels/Pixabay
N95 masks without valves are most effective at protecting against the new coronavirus, followed by surgical or polypropylene masks, researchers say. Photo by RevsReels/Pixabay

When it comes to face masks, not all are equally effective, a new study finds.

Duke University researchers developed a way of testing various types of masks to see which did the best job of stopping droplets coming from people's mouths, preventing spread of the new coronavirus.

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They relied on a makeshift apparatus consisting of a box, a laser, a lens and a cellphone camera.

"We confirmed that when people speak, small droplets get expelled, so disease can be spread by talking, without coughing or sneezing," said Martin Fischer, a chemist and physicist at the Durham, N.C., campus. "We could also see that some face coverings performed much better than others in blocking expelled particles."

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What masks do the best job? That would be N95 masks without valves, followed by surgical or polypropylene masks.

Handmade cotton masks also stop a lot of droplets from normal speech, researchers said.

But bandanas and neck fleeces like balaclavas didn't block saliva spray much at all.

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"This was just a demonstration -- more work is required to investigate variations in masks, speakers, and how people wear them," Fischer said in a university news release. He added it demonstrates that businesses and others that are providing masks to employees or patrons could do similar testing.

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"If everyone wore a mask, we could stop up to 99% of these droplets before they reach someone else," said Dr. Eric Westman, an associate professor of medicine at Duke. "In the absence of a vaccine or antiviral medicine, it's the one proven way to protect others as well as yourself."

The report was published online Aug. 7 in the journal Science Advances.

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More information

For more on COVID-19 face masks, visit the U.S. Centers for Disease Control and Prevention.

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