Science has told us, again and again, that you should wear a face mask to help prevent the spread of COVID-19. However, we don’t hear as much about what kind of face masks are best. And that’s a shame, because a new study published by Duke University researchers in Science Advances has found significant differences among the options — and that one particular type, the outdoorsy neck gaiter, may in fact be counterproductive.
First, a quick reminder why face masks are so important: Every time we speak, we emit respiratory droplets that can transmit the virus. Face masks restrict the spread of those droplets, reducing the chance of asymptomatic carriers unknowingly passing along COVID-19. It’s not about you, it’s about everybody else.
Duke University researchers used an optical imaging approach — involving a laser and a camera — to test the differences in effectiveness of 14 types of face coverings, including N95 masks, surgical masks, knitted masks, cotton masks, bandanas and gaiters. While the study’s goal was to demonstrate how simply such a setup can be constructed, the findings are worth noting, particularly the problematic nature of gaiters.
The researchers found that the neck gaiter — a sun-protection staple that was never designed or intended as a coronavirus-fighting measure — actually disperses the largest respiratory droplets into multiple smaller droplets, which stay airborne longer because large droplets sink faster. In other words, speaking through one of these masks seems to create a lighter, longer-lasting, virus-carrying army.
While the study did not disclose the brand and model of the gaiter tested, it's important to recognize that the type of material likely makes more of a difference than the shape, notes Martin C. Fischer, Ph.D., an associate research professor in chemistry and physics at Duke.
"The [neck gaiter] we demonstrated was a polyester/spandex mask," he explained via email. "Typically, these masks are pretty thin to provide breathability, which is likely the reason for lots of particles getting through, broken into smaller pieces. However, we expect that there are variations of performance for different masks (even of the same type), and different users wearing identical masks."
Bandanas also demonstrated very limited effectiveness, while fitted N95 masks, three-layer surgical masks and masks that can accommodate polypropylene filters were the most effective at curtailing droplets, followed by a variety of relatively standard two-layer cotton masks.
This study’s findings go against what some experts have hypothesized for months, namely that gaiters can provide adequate coverage against the spread of coronavirus. In fact, Dr. Abraar Karan, a physician at Harvard Medical School, recently told NPR that, with gaiters, "there would theoretically be less chance for the air to escape laterally out of the sides like it would from a mask that's open on the side."
While more research certainly needs to be done, the new study raises serious questions about gaiters made from light, stretchy, single-layer microfiber material. That may explain why perhaps the most famous purveyor of this type of product, Buff, now also makes a filter mask.