Coughing More Than Once May Make Face Masks Less Effective, Study Says

Along with social distancing, wearing face masks is thought to help slow or prevent the spread of COVID-19. The reason being, when an infected person coughs, sneezes, or spits while talking, the mask may block the respiratory droplets from traveling onto someone else. However, a recent study, published in an issue of Physics of Fluids, suggests that while masks may work against one cough, they’re less effective when someone coughs repeatedly.

Researchers from the University of Nicosia in Cyprus used computer simulations to replicate the flow patterns of respiratory droplets from repetitive coughing behind a face mask. With each cough, the mask became less effective at preventing the spread of airborne droplets.

While previous research has shown that certain face masks can filter respiratory droplets, those filtering abilities become less effective when coughing is repetitive.

More specifically, after 10 cough cycles, the mask efficiency can drop by about 8%, the study says. The coughs tested in this experiment were considered mild. “We should expect a more significant efficiency reduction for severe coughing events, as well as when wearing a mask for a longer period,” the study writes.

That said, masks still reduce the distance in which airborne droplets are able to travel. Without a mask, they traveled almost 1 meter, but that number was cut in half when masks were worn. It also limited the number of droplets being spread.

In short, yes. Masks can at least reduce the number of escaped droplets, and they shorten the distance that they spread.

Understanding that masks cannot provide complete prevention of transmission is important in both indoor and outdoor settings, the study says, since wind can carry droplets several meters away. Social distancing also remains essential, researcher Dimitris Drikakis, Ph.D., says.

Wearing cloth or surgical face coverings may limit the distance and level of transmission, but they do not completely stop respiratory droplets from spreading. Continuing to practice social distancing, wearing masks as often as possible, and staying home when you’re sick are critical steps to help prevent viral spread—especially as businesses begin to reopen.