Wearing two well-fitted face masks can double the effectiveness of filtering 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 improved filtration is not so much the addition of layers of cloth as the elimination of any gaps or poorly matched areas of a mask.
“Medical procedure masks are designed to have very good filtering potential based on their material, but the way they fit our faces is not perfect,” said Emily Sickbert-Bennett, an associate professor at the University of North Carolina. UNC) in the USA and the lead author of the study. To test the mounted filtration efficiency (FFE) of a range of masks, the team filled a 10-foot by 10-foot stainless steel display chamber with aerosols with small 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 layered mask combination was fitted with a metal sample port attached to the tubing in the exposure chamber that measured the concentration of particles entering the breathing space under the researcher’s mask. A second tube measured the ambient concentration of particles in the chamber.
The researchers determined FFE by measuring the concentration of particles in the breathing space under the mask compared to that in the room. “Also, the researchers in the room underwent a series of movement activities to simulate the typical movements that a person can make throughout the day – bending at the waist, talking and looking left, right, up and down, “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 the unique fit of the face and mask of each individual. In general, a procedure mask without changing the fit is about 40-60 percent effective at maintaining particles the size of COVID-19, the researchers said. A cloth mask is about 40 percent effective, they said. Their latest findings on doubling face masks show that when a cloth mask is placed over a surgical mask, FFE has improved by about 20%.
The filtration efficiency has been further improved with a perfect, sleeve-like mask, according to the researchers. When layered over procedure masks, cloth masks improve fit by eliminating gaps and keeping the procedure mask closer to the face, constantly covering the nose and mouth. When a procedure mask is worn over a cloth mask, the FFE improved by 16%.
“We’ve found that wearing two lightly mounted masks won’t give you the benefit of filtering a single procedure mask,” said Sickbert-Bennett. “And with current data supporting how effective it is to wear a mask to prevent the spread of COVID-19, the best type of double-sided mask is when you and the person you are interacting with are wearing the right mask,” she added.