Scientists now report that wearing two face coverings can nearly double the effectiveness of filtering out SARS-CoV-2-sized particles, preventing them from reaching the wearer’s nose and mouth and causing Covid-19.<\/p>\n
The reason for the enhanced filtration isn’t so much adding layers of cloth but eliminating any gaps or poor-fitting areas of a mask, according to the study published in JAMA Internal Medicine.<\/p>\n
“The medical procedure masks are designed to have very good filtration potential based on their material, but the way they fit our faces isn’t perfect,” said Emily Sickbert-Bennett, associate professor of infectious diseases at the University of North Carolina (UNC) School of Medicine and lead author of the study.<\/p>\n
To test the fitted filtration efficiency (FFE) of a range of masks, the researchers worked with James Samet and colleagues in the USEPA Human Studies Facility on the campus of UNC-Chapel Hill.<\/p>\n
There they filled a 10-foot by 10-foot stainless-steel exposure chamber with small salt particle aerosols, and had researchers don combinations of masks to test how effective they were at keeping particles out of their breathing space.<\/p>\n
By measuring particle concentration in the breathing space underneath the mask compared to that in the chamber, researchers determined the FFE.<\/p>\n
“We also had the researchers in the chamber undergo a series of range-of-motion activities to simulate the typical motions a person may do throughout their day, bending at the waist, talking, and looking left, right, up and down,” said Phillip Clapp, an inhalation toxicologist in the UNC School of Medicine.<\/p>\n
According to their findings, the baseline fitted filtration efficiency (FFE) of a mask differs person to person, due to each person’s unique face and mask fit.<\/p>\n
Generally, a procedure mask without altering the fit, is about 40-60 per cent effective at keeping Covid-19-sized particles out. A cloth mask is about 40 per cent effective.<\/p>\n
When layered over procedure masks, cloth masks improve fit by eliminating gaps and holding the procedure mask closer to the face, consistently covering the nose and mouth.<\/p>\n
When a procedure mask is worn over a cloth mask, FFE improved by 16 per cent.<\/p>\n
“We’ve found that wearing two loosely fitted masks will not give you the filtration benefit that one, snug-fitting procedure mask will,” Sickbert-Bennett said.<\/p>\n","protected":false},"excerpt":{"rendered":"
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