Study: Locally made masks effective
Tennessee took a lot of flak for the free masks it began distributing this month, with critics saying the socklike material the masks are made of wouldn’t be effective at stopping the spread of coronavirus.
Social media critics were bashing the masks on sight alone, though, so the Knoxville News Sentinel decided to put them to the test. The newspaper enlisted Northeastern University engineering professor Amy Mueller — she’s running a cloth mask testing project.
The masks made by sock manufacturer Renfro Corp., it turns out, can be as effective as surgical masks in some cases.
Mueller’s study examines how well cloth masks filter out airborne particles and compares them to surgical masks and N95 respirators. According to Mueller’s study, Tennessee’s masks can effectively filter 57-63% of small, airborne particles, putting them in the same neighborhood as surgical masks, which tested at 53-75% effective. N95 masks were able to filter out 99% of test particles.
Other cloth masks varied widely in filtration effectiveness. They ranged from 47-90% effective. Tennessee’s masks sit squarely in the middle of a big pack.
Mueller’s team also tested whether tightening cloth masks would improve filtration. This is done by layering nylon stocking over the masks like a neck gaiter. Tennessee’s masks did not improve
when tightened, which suggests they might have a good flexible fit. In comparison, surgical masks improved to 86-90% filtration when tightened with nylons.
“Given that we saw this has a relatively good fit to the face, I would expect that filtration number for small particles at least to be in the same ballpark for inhalation or exhalation,” Mueller said by email. “However the exact efficiency as personal health protective equipment should be measured by a materials testing lab to confirm this.”
Mueller’s study is ongoing, and the data is preliminary. It is far from the final word on which mask material is best, and other factors, like comfort, come into play. The masks distributed by the state are light and breathable and easily washed.
The tests were also conducted on new, out-of-the-package masks. Whether
this material holds up after repeated use is still unknown (although in any case it’s best to wash your mask after use).
The state intends to purchase 5 million of the masks from Renfro. The North Carolina-based international sock distributor has a Cleveland, Tennessee, manufacturing and distribution plant.
Social distancing and minimizing exposure are still recommended even if everyone was wearing the masks or equivalent ones.
The science behind whether masks prevent the spread of COVID-19 is still unclear. Standards for how effectively cloth masks should catch droplets from the wearer’s mouth have not been developed.
The Centers for Disease Control and Prevention recommends the public wear cloth masks to help prevent asymptomatic transmission in areas where social distancing might not be possible, like a grocery store aisle. This also reduces stress on the medical supply chain. It’s a precautionary measure.