Scientists at the University of North Carolina School of Medicine have investigated the effectiveness of various face masks and consumer modified masks against Covid-19 in collaboration with the Environmental Protection Agency.
The researchers used a methodological approach based on OSHA’s fit testing to determine the effectiveness of various masks based on their adjusted filtration efficiency (FFE).
The researchers studied seven consumer masks and five medical procedure mask modifications. These masks were placed on an adult male. The researchers collected FFE measurements from the masks during a series of repeated movements of the torso, head, and facial muscles, as described in OSHA’s Quantitative Fit Testing Protocol.
The research found that, in terms of consumer masks, some masks, such as a two-layer woven nylon mask, nose bridge earmuffs, washed without insert, were 79 percent effective in blocking particles that could carry the virus . A similar mask with a nonwoven insert had an efficacy of 74.4%.
The three-layer woven cotton mask with ear hooks was found to be the least effective at blocking particles with 26.5 percent efficiency.
The unmodified medical procedure masks with ear muffs offered a filtration efficiency of 38.5%. However, when the earmuffs were tied in a specific way to adjust the fit, the mask’s effectiveness increased to 60.3 percent. Adding a layer of nylon to these masks was 80 percent effective.
Cotton bandana or folded Surgeon General style masks offered 50 percent filtration.
The NIOSH approved N95 3M 9210 Respiratory Mask was found to be 98 percent effective.
Specific details of the efficacy of these masks with details on the filtration ability of various masks can be found in a study published in the journal JAMA Internal Medicine.
“While modifications to surgical masks can improve filtering capabilities and reduce inhalation of airborne particles by improving mask fit, we demonstrated that the adjusted filtration efficiencies of many consumer masks were nearly equivalent to or better than surgical masks, “said co-author Phillip Clapp, PhD, inhalation toxicologist and assistant professor of pediatrics at UNC School of Medicine.
Co-first author Emily Sickbert-Bennett, PhD, director of infection prevention at UNC Medical Center, said: “Limiting the amount of virus is important because the more virus particles we are exposed to, the more likely we are to sick and potentially seriously ill. “