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With facemask donations pouring in and a proliferation of instructional videos for fabricating masks at home, UNC and EPA researchers are collaborating with infection prevention experts to test the performance of masks on campus, with the goal of providing UNC Health workers with the safest available masks at all times. The research collaboration is led by Emily Sickbert-Bennett, PhD, and Phillip Clapp, PhD.

Due to limited national supplies of N95 facemasks, hospitals across the country have been accepting public and private company donations of personal protective equipment, including many different types of masks. At the same time, creative do-it-yourselfers are providing guidance online for how to make face coverings at home, as well as how to improve the efficiency of underperforming masks. With so many options, infection prevention experts at the UNC Medical Center set out to gather evidence on the fitted aerosol filtering efficiency of dozens of different types of masks and mask modifications, including masks sterilized for reuse, expired masks, novel masks sourced from domestic and overseas sources, and homemade masks.

To test the efficacy of these alternatives, Emily Sickbert-Bennett, PhD, director of infection prevention at UNC Medical Center and colleagues turned to someone she knew she could trust: her dad, William Bennett, PhD, Professor of Medicine, who leads the Mucociliary Clearance and Aerosol Research Laboratory at the UNC Center for Environmental Medicine, Asthma, and Lung Biology (CEMALB).

“Over dinner several weeks ago I told him we had both sterilized and expired masks and we needed to know whether they would offer safe and effective protection,” Sickbert-Bennett said. “And he said it should be possible for his lab to test them and give us data upon which to base our decision-making.”

Hao Chen, William Bennett, Kirby Zeman, Phillip Clapp, and James Samet are part of the team testing the efficacy of a different face masks.
Hao Chen, William Bennett, Kirby Zeman, Phillip Clapp, and James Samet are part of the team testing the efficacy of different face masks.

Thanks to a cooperative agreement with the EPA Human Studies Facility located on Mason Farm Rd, in which Dr. Bennett’s labs reside, Dr. Bennett, toxicologist Phillip Clapp, PhD, postdoctoral research associate, and Dr. Kirby Zeman, research associate, teamed with EPA research scientist, James Samet, PhD, to measure the fraction of submicron particles that penetrate into the breathing space of subjects wearing a mask while performing a series of tasks that simulate conditions such as speech and movement during a work shift. Such data provided infection prevention leaders quantitative data they used to rank the best respiratory protection options for healthcare during the COVID-19 outbreak.

To date, this team of researchers has found that certain NIOSH-rated N95 masks retain greater than 95 percent effectiveness at keeping out the smallest size of airborne particles that could carry SARS-CoV-2 – the virus that can cause COVID-19 – many years beyond their expiration date. Similarly, these masks can be subjected to sterilization with hydrogen peroxide or ethylene oxide without compromising their efficiency.

“Our hierarchy of mask supplies essentially amounts to always using the safest option on the shelf,” Sickbert-Bennett said. “We start with products of our usual make/model, then follow with CDC/FDA/NIOSH approved products, and then we plan to reintroduce sterilized masks before we consider using non-CDC approved products that perform at less than 95 percent effectiveness levels.”

Dr. Clapp also led the group to test other masks and homemade creations, using the same chamber and aerosol measurement equipment used for testing the commercial masks.

“I saw this YouTube video recommending a mask made from blue shop paper towels, the kind you can buy at Lowes or Home Depot,” Clapp said. “I mentioned in the comments section I could test his mask, and the guy who made the video was all for it.”

Turns out single-layer shop paper towels fashioned into masks with a rubber band behind the neck or with ear loops are about 54 percent effective. A double-layer shop paper towel mask is about 74 percent effective. Clapp said this percent effectiveness is surprisingly good among homemade masks.

“One of the keys to protection is how snug a mask fits,” Sickbert-Bennett said. “An N95 mask that forms a tight seal offers optimal infection prevention.”

UNC Health infection prevention leaders are grateful for the partnership with the Center for Environmental Medicine, Asthma, and Lung Biology (CEMALB) and the EPA Human Studies Facility on Mason Farm Rd. Thanks to this collaboration UNC Health can make evidence-based decisions on how to best protect our co-workers.

A Q and A with Phillip Clapp, along with a video about homemade masks based on his research, can be found at the UNC Office of Research Communications website.

Written by Mark Derewicz, UNC Health Director of Research News.