NEW YORK :
SCIENTISTS now report that wearing two face covers can nearly double the effectiveness of filtering out SARS-CoV-2 particles, preventing them from reaching the wearer’s nose and mouth and causing COVID-19. The reason behind the improved filtration isn’t so much because of adding layers of fabric, but rather to remove gaps or poorly fitting areas of a mask, according to the study published in JAMA Internal Medicine.
“The medical treatment masks are designed to have very good filtration potential because of their material, but the way they fit our faces is not 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. To test the Adapted Filtration Efficiency (FFE) of a range of masks, researchers worked with James Samet and colleagues at the USEPA Human Studies Facility on the UNC-Chapel Hill campus. There, they filled a 10-foot by 10-foot stainless steel exposure chamber with aerosols of small salt particles and had researchers put on combinations of masks to test how effective they were at keeping particles out of their breathing space.
By measuring the particle concentration in the breathing space under the mask compared to that in the chamber, the researchers determined the FFE. “We also had the researchers do a series of range of motion activities in the chamber to simulate the typical movements a person can make during their day, bending at the waist, talking, and left, right, up and down looking down. ” said Phillip Clapp, an inhalation toxicologist at the UNC School of Medicine. According to their results, the Baseline Adjusted Filtration Efficiency (FFE) of a mask differs from person to person due to the individual face and mask fit of each person.