Covid-19: Scientists test effectiveness of consumer-grade masks and improvised face coverings

Scientists at the University of North Carolina’s School of Medicine have researched the effectiveness of various consumer-grade face masks and modified masks against Covid-19 in collaboration with the Environmental Protection Agency.

Researchers used a methodological approach based on the OSHA Fit Test to determine the efficacy of various masks based on their fitted filtration efficiency (FFE).

Researchers studied seven consumer-grade masks and five medical procedure mask modifications. These masks were fitted on an adult male. Researchers collected FFE measurements of the masks during a series of repeated movements of the torso, head, and facial muscles as outlined by the OSHA Quantitative Fit Testing Protocol.

The research found that in terms of consumer-grade masks, some masks such as a two-layered woven nylon mask, ear loops with nose bridge, washed with no insert were 79 per cent effective at blocking particles that could carry the virus. A similar mask with one non-woven insert was 74.4 per cent effective.

Three-layer woven cotton mask with earloops was found to be the least effective in blocking the particles with 26.5 per cent efficacy.

Unmodified medical procedure masks with ear loops offered 38.5 per cent filtration efficacy. However, when the ear loops were tied in a specific way to tighten the fit, the efficacy of the mask increased to 60.3 per cent. Adding a layer of nylon to these masked offered 80 per cent effectiveness.

Cotton bandana or folded Surgeon General style masks offered 50 per cent filtration.

The 3M 9210 NIOSH-approved N95 Respirator mask was found to be 98 per cent effective.

Specifics of the efficacy of these masks with details regarding the filtration capacity of various masks can be found in a study published in the journal JAMA Internal Medicine.

"While modifications to surgical masks can enhance the filtering capabilities and reduce inhalation of airborne particles by improving the fit of the mask, we demonstrated that the fitted filtration efficiencies of many consumer-grade masks were nearly equivalent to or better than surgical masks," said co-first author Phillip Clapp, PhD, an inhalation toxicologist and assistant professor of paediatrics at the UNC School of Medicine.

Co-first author Emily Sickbert-Bennett, PhD, director of infection prevention at the UNC Medical Center, said, "Limiting the amount of virus is important because the more viral particles we're exposed to, the more likely it is we will get sick and potentially severely ill."