SAN ANTONIO – As face coverings become an essential part of everyday life during the coronavirus pandemic, researchers are saying that some options may be counterproductive.
Researchers from Duke University published a study on Friday that focused on commonly available face masks and coverings, and how efficient they are in protecting people from infection.
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They found cotton masks have a strong effect, but bandanas, not so much. With neck fleece, or gaiter-type neck coverings, those could be as ineffective as not wearing a mask at all, or even worse.
“We noticed that speaking through some masks (particularly the neck fleece) seemed to disperse the largest droplets into a multitude of smaller droplets, which explains the apparent increase in droplet count relative to no mask in that case,” the study published in Science Advances magazine states.
“Considering that smaller particles are airborne longer than large droplets (larger droplets sink faster), the use of such a mask might be counterproductive.”
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Researchers tested 14 different coverings, including bandanas and surgical, knitted, valved N95, fitted N95, cotton, and fleece masks. Each option was tested 10 times.
Mask wearers spoke into the direction of a laser beam in a dark enclosure. Any droplets that propagated through the laser beam scattered light, which was recorded by a cell phone camera, the study says. Droplets were counted in a computer algorithm.
The droplet transmission ranged from below 0.1% with a fitted N95 mask to 110% with a fleece mask, the study says.
Surgical, cotton-polypropylene-cotton and 2-layer polypropylene apron masks followed fitted N95s as the most effective.
The experts say while the experiment is straightforward, there are limitations.
“Inter-subject variations are to be expected, for example due to difference in physiology, mask fit, head position, speech pattern, and such,” the study states.
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The co-founder of one gaiter manufacturer, Vapor Apparel, told The Washington Post that the face-covering option shouldn’t be dismissed entirely.
“All gaiters are not created equal,” Chris Bernat of Vapor Apparel said. “There’s a segment of this category that’s of a much higher quality that’s engineered to be layered.”
The study found bandanas and knitted masks were among the least effective.