Wearing two tight-fitting face masks 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, according to a study. The research, published in the journal JAMA Internal Medicine, shows that the reason for enhanced filtration is not so much the addition of tissue layers, but the elimination of any gaps or areas of poor fit of a mask.
“Medical procedure masks are designed to have great filtration potential based on their material, but the way they fit our faces isn’t perfect,” said Emily Sickbert-Bennett, associate professor at the University of North Carolina (UNC) in the United States and lead author of the study. To test the Matched Filtration Efficiency (FFE) of a range of masks, the team filled a 10-foot-by-10-foot stainless steel exposure chamber with small aerosols of salt particles.
The researchers wore a combination of masks to test how effective they were at keeping particles out of their breathing space. Each individual mask or combination of layered masks had a metal sampling port attached to the tube in the exposure chamber that measured the concentration of particles entering the respiratory space under the researcher’s mask. A second tube measured the ambient concentration of particles in the chamber.
The researchers determined EBF by measuring the concentration of particles in the respiratory space under the mask relative to that in the chamber. “We also had the researchers in the chamber perform a series of movement activities to simulate the typical movements a person may do throughout the day: bending at the waist, speaking and looking left, right, up and down,” he said. said Phillip Clapp of the UNC School of Medicine.
According to their findings, the basic FFE of a mask differs from person to person, due to each individual’s unique face and mask fit. In general, a procedure mask without altering fit is about 40 to 60 percent effective in keeping COVID-19-sized particles away, the researchers said. A cloth mask is about 40% effective, they said. Their latest findings on doubling face masks show that when a tissue mask is placed over a surgical mask, the FFE is improved by about 20%.
According to the researchers, filtration efficiency is improved even more with a tight-fitting mask with sleeves, like a gaiter. When superimposed on procedural masks, cloth masks improve fit by eliminating gaps and keeping the surgical mask closer to the face, constantly covering the nose and mouth. When a procedure mask is worn over a cloth mask, FFE is improved by 16%.
“We found that wearing two loosely fitted masks won’t give you the filtration advantage that a tight-fitting procedure mask,” Sickbert-Bennett said. “And with current data supporting the effectiveness of wearing the mask in preventing the spread of COVID-19, the best type of double masking is when you and the person you’re interacting with are wearing a very tight mask correctly,” she said. added.