The mask with the valve performed as expected — sending unfiltered droplets into the surrounding air.
“Over time, these droplets can disperse over a wide area in both lateral and longitudinal directions, albeit with decreasing droplet concentration,” researcher Manhar Dhanak, a professor at FAU, said in a statement from the university.
The standard mask, on the other hand, did a much better job of containing droplets — allowing fewer to be expelled and limiting their spread. (The tests involved “surgical” masks that are marketed to the public and not recommended for medical use.)
The study, published Sept. 1 in the journal Physics of Fluids, did not test any face coverings’ ability to prevent transmission of SARS-CoV-2, the virus that causes COVID-19.
In the real world, that would depend on many factors, said Dr. Gregory Poland, an infectious disease specialist at the Mayo Clinic, in Rochester, Minn.
The droplets that elude a face covering would have to contain infectious virus — and expose another person to a big enough “load” of those particles — to transmit the disease, he explained.
That said, the disadvantages of the face shield are obvious — including for the wearer, according to Poland. “Air is drawn in and under,” he said. “You increase the chances of breathing in whatever is in the ambient air.”
Like Kullar, Poland is in favor of the mask-shield combination. But as a stand-alone, he said, the face shield is “the least successful option.”
Of course, cloth masks only work if they are worn properly.
“Don’t wear it under your nose,” Poland stressed. Leaving the nose exposed in public settings “is the riskiest thing you can do,” he said.
And while mask-wearing is important, Kullar said that alone does not cut it: Maintaining physical distance from other people remains critical — including outdoors.
“I don’t think we emphasize that message strongly enough,” Kullar said. “The risk is lower outdoors than indoors, but the risk is still there.”
WebMD News from HealthDay
Sources
SOURCES: Ravina Kullar, PharmD, MPH, adjunct faculty, David Geffen School of Medicine, University of California, Los Angeles, and spokesperson, Infectious Diseases Society of America, Arlington, Va.; Gregory Poland, MD, professor, medicine, and director, Vaccine Research Group, Mayo Clinic, Rochester, Minn.;Physics of Fluids, Sept. 1, 2020, online
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Source: https://www.webmd.com/lung/news/20200901/face-shields-no-good-as-substitute-for-masks-study-shows?src=RSS_PUBLIC