Study shows that adding filter layer, drying masks maximizes effectiveness
Drying face masks and adding an additional layer of filtration are among the best ways to maximize their effectiveness against COVID-19, according to research by two Kent State University professors in partnership with the Kent City Health Department and Kent Fire Department.
Two articles on their research were published in the scientific journal “Applied Biosafety” recently. The first article studied methods of using silica beads to dry N95 respirators, ridding them of exhaled, moist air that accumulates when the masks are worn for extended periods.
Dr. Christopher Woolverton, a professor of epidemiology in the College of Public Health, and Summit Professor of Learning Technologies Dr. Richard E. Ferdig, a professor of educational technology, worked on the articles with Kent Health Commissioner Joan Seidel and the fire department on the first article.
Drying cloth masks after washing them is an important step in mitigating the virus. Woolverton said the coronavirus differs from some other viruses, which get released from their host cells by a process known as “budding.” The protein-bound virus pushes against the host cell membrane until the virus pushes hard enough to overcome the resistance, thus escaping the cell.
However, the coronavirus retains the host membrane and seals and uses it as an external protective layer for the virus. The outside of the membrane contains the binding proteins necessary for the virus to infect another host cell. If the membrane is degraded by detergents, alcohol or drying, then the remaining “naked” virus can no longer infect host cells. Thus, drying face coverings would help eliminate the infectious viruses, they conclude.
“As a microbiologist, I know, based on other virus studies, that once the textile is completely dry, the COVID virus degrades and becomes noninfectious,” Woolverton said. “Drying textiles should analogously inactivate membrane-bound viruses, and COVID is a membrane-bound virus.”
Ferdig and Woolverton also worked with doctoral students in nursing and public health to publish information on the use of surgical wrap fabrics made into masks. They have reported on the ability of these materials to act as suitable substitutes, some with better protective capabilities, for existing cotton or cotton/polyester face masks. They are also researching adding fillers or filters to other textiles to make masks more effective.
“Having face-covering alternatives and methods to rapidly reuse them is essential in the fight against the virus,” Woolverton said.
According to Woolverton, they have examined four different weaves of textiles and found that they have increased the ability to prevent particles from passing through them.
“None of them are as good as an N95 mask, but they can be used by nonmedical folks who shouldn’t be using N95s anyway,” he said.
Ferdig and Woolverton’s research transitioned from their original research, which focused on how to find replacement PPE for healthcare workers during a time when there was a shortage of PPE.
“Since that time, and with the ability to have more PPE, our research has focused more on the quality of materials being used for masks,” Ferdig said. “Our research is important because there is limited work in that area. We are one of a few studies not directly comparing commercial products but actual materials used for PPE generation.”
Woolverton recommends using a textile that is two-ply and composed of cotton and polyester. The mask should have a pocket between the plies for the insertion of additional filtering textiles to be added during times of increased exposure to the virus (for example, while on public transportation).
When washing masks, the filtering materials should be thrown away prior to washing with new material being added afterward.
The COVID-19 virus can stay in masks when they are wet from exhaled, moist breath. Washing and drying the cloth face coverings should inactivate any coronavirus that might have landed on the mask during its use.
Tips for mask use and cleaning
The professors also offer a variety of tips for mask use and cleaning.
• Do not overwear masks.
• Wash masks daily.
• For additional protection, most masks have a space for adding materials or filtering textiles. Fill those pockets with 50% cotton, 50% polyester blends.
• Make sure the mask fits. Masks that are not as effective as one that fits snugly.
• Disposable masks should be used for three to four hours unless they’re excessively contaminated. In that case, dispose them immediately.
• Discard N95 masks with damage, broken straps or if there is increased breathing difficulty, which can indicate clogging.
• Always wash and sanitize hands after removing any mask or face covering designed to prevent virus transmission.
Reporter Bob Gaetjens can be reached at firstname.lastname@example.org and @bobgaetjens_rc.