Research: Wearing a double-layer mask can nearly double the efficiency of protection against COVID-19

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“Although medical masks are designed to have very good filtering capabilities based on their materials, the way they fit on our faces is not perfect,” from the Associate Professor of Infectious Diseases at the University of North Carolina (UNC) School of Medicine and the main researcher Author Dr. Emily Sckbert-Bennett said.

To test the filtration efficiency (FFE) of a series of masks, UNC researchers collaborated with Dr. James Samet and colleagues at the U.S. Environmental Protection Agency’s Human Research Facility at the University of North Carolina at Chapel Hill. There, they filled a 10-foot x 10-foot stainless steel exposure chamber with small salt particle aerosols and asked the researchers to wear a combination mask to test their effectiveness in keeping the particles out of the breathing space.

Each individual mask or layered mask combination is equipped with a metal sample port, which is connected to a tube in the exposure chamber, which is used to measure the amount of air entering the breathing space under the researcher’s mask. Particle concentration. The other tube is used to measure the concentration of particles in the room. Researchers determine the FFE value by measuring the particle concentration in the breathing space under the mask and comparing it with the particle concentration in the laboratory.

Research: Wearing a double-layer mask can nearly double the efficiency of protection against COVID-19

“We also let researchers in the laboratory A series of exercise activities are performed inside to simulate the typical exercise that a person might do in a day. Bend over, talk, look left and right, look up and down,” said Dr. Phillip Clapp, an inhalation toxicologist at the UNC School of Medicine. Since the beginning of the pandemic, he has been testing FFE masks with Sickbert-Bennett.

According to their findings, due to each person’s unique face and the adaptability of the mask, the baseline adaptive filtration efficiency (FFE) of the mask varies from person to person. But generally speaking, without changing the comfort level, the effectiveness of procedural masks in preventing COVID-19-sized particles from entering the body is about 40-60%. The effectiveness of cloth masks is about 40%.

A recent finding by the research team on doubling the use of masks shows that when a cloth mask is worn on a surgical mask, FFE is increased by about 20%, and when a fitted sleeve mask is used, FFE The improvement is even greater. When the surgical mask was worn on a cloth mask, FFE increased by 16%.

Sickbert-Bennett pointed out: “We found that wearing two loose masks cannot achieve the filtering effect of one loose mask. Current data supports that wearing masks is very effective in preventing the spread of COVID-19, and it is best. The double-layer mask is a very comfortable mask when you and the people you come into contact with are correctly wearing a very comfortable mask.”