“We are not defenseless against covid-19,” Robert R. Redfield, director of the Centers for Disease Control and Prevention. “Cloth face coverings are one of the most powerful weapons we have to slow and stop the spread of the virus – particularly when used universally within a community setting.”
But as face coverings have become increasingly commonplace in American life, so have questions about efficacy — and now a group of researchers from Duke University are aiming to provide some answers.
“You can really see the mask is doing something,” said one of the study’s co-authors, Warren S. Warren, a professor of physics, chemistry, radiology and biomedical engineering at Duke. “There’s a lot of controversy and people say, ‘Well, masks don’t do anything.’ Well, the answer is some don’t, but most do.”
The search for a way to determine the effectiveness of different masks began with a request from a professor at Duke’s medical school who was working to provide at-risk and underserved populations in Durham, N.C., with the critical face coverings, according to a news release from the university. Faced with so many varieties of masks all claiming to have virus-blocking capabilities, the professor sought help — in the university’s physics department.
Using a simple contraption that harnesses the power of a laser, which can be easily purchased online for less than $200, and a cell phone camera, Fischer created a device that allowed his team to track individual particles released from a person’s mouth when they are speaking. The rest of the setup includes a box that can be made out of cardboard and a lens.
“It’s very straightforward, doesn’t take much resources,” Fischer said in a video produced by Duke. “Any research lab has these things lying around.”
Testing the face coverings was equally uncomplicated, according to the study published Friday in Science Advances, a peer-reviewed journal.
A fitted N95 mask, which is used most commonly by hospital workers, was the most effective, Warren said, noting that the mask allowed “no droplets at all” to come out. Meanwhile, a breathable neck gaiter, well-liked by runners for its lightweight fabric, ranked worse than the no-mask control group. The gaiter tested by the researchers was described in the study as a “neck fleece” made out of a polyester spandex material, Warren said.
“Buff performance head and neckwear are not intended to be used as medical-grade face masks or as a replacement for N95 respirators as effective measures to prevent disease, illness, or the spread of viruses,” the statement said.
“All gaiters are not created equal,” Chris Bernat, co-founder of South Carolina-based Vapor Apparel, said. “There’s a segment of this category that’s of a much higher quality that’s engineered to be layered.”
“It’s not the case that any mask is better than nothing,” he said. “There are some masks that actually hurt rather than do good.”
“Those relief valves are fantastic if what you want to do is protect yourself from the outside world because air doesn’t come in through them,” Warren said. “If what you’re trying to do in this pandemic is protect the outside world from you, it completely defeats the purpose.”
Warren encouraged people to assess their face coverings with another basic test.
“If you can see through it when you put it up to a light and you can blow through it easily, it probably is not protecting anybody.”
“We’re not as a society going to be having everybody wear disposable N95 face masks,” he said. “It’s not affordable, and it’s not reasonable.” The researchers specifically made note of the effectiveness of common cotton cloth masks, finding that several of the ones tested performed about as well as surgical masks, which come in second to the N95. Experts with the WHO have recommended that fabric masks should ideally have three layers.
“We’re very careful not to over-claim here,” he said. “We are not going to try to say our evidence is that this is the thread count you should use on the sheet for the two-ply cotton mask that you’re making.
Warren said he and his fellow researchers are now focused on producing a step-by-step instruction guide for creating the testing device. The team has already been approached by people from foreign countries who have expressed interest, he said.
“It is quite possible for people with a modest amount of scientific training to use this quite safely and quite effectively,” Warren said, noting that he does not recommend that the average person go out and try to construct the device themselves. “The idea is that you could have community centers, groups that are helping to test out different designs. Particularly as we’re trying to provide face masks to a large number of people who don’t have them, you want to be providing ones that work.”