Study shows most homemade masks help slow coronavirus droplets

A new study adds to the growing evidence that masks of almost any type will help slow and stop the spread of the coronavirus.

The study from Duke University researchers, published in the journal Science Advances, found that most types of homemade masks are better at preventing the spread of droplets than nothing at all, but the effectiveness largely depends on their material and fit.

Researchers tested 14 different types of masks, ranging from N95 surgical respirators to cotton masks and bandanas. The fitted N95 was the most effective at preventing droplets emitted during talking, while plain paper surgical masks were also extremely effective.

Cotton masks performed better when they had more layers, while a breathable fleece neck gaiter actually performed worse than no mask at all.

In a video accompanying the study, Martin Fischer, a Duke associate research professor of chemistry and physics, said the poor performance of the gaiter could be due to the fleece fabric.

The fleece tended to break up the larger droplets into smaller droplets that are more likely to hang around in the air longer, Fischer said.

This could make wearing them possibly “counterproductive,” Fischer said.

“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.”

Valved N95 masks, which allow for the wearer to exhale, performed significantly worse than non-valved N95 masks. 

While the valve does not compromise the protection of the wearer, it can decrease protection of other people, since the valve allows droplets to spread.

However, Fischer and the other researchers noted the study was mainly meant to show that their method of testing masks worked, not necessarily to draw conclusions from the results. 

The study itself was very limited. 

The number of testers was small, and four people tested three materials (a surgical mask, a cotton mask and a bandana). But only one person tested the other 11 materials, including the neck gaiter. 

One of the study’s co-authors told The Washington Post the gaiter was made out of a “polyester spandex material,” but the journal publication did not include detailed descriptions of the materials. 

There were also considerable differences in the baselines of speaking without masks among individual testers. 

Fischer said the basic conclusion is that wearing masks is better at slowing the spread of airborne droplets than not, and some masks are better than others.

“It gives you a good idea of how the mask actually performs in general,” Fischer said. “We certainly encourage everyone to wear a mask, but you want to make sure when you wear a mask and you go through the trouble of making a mask, you make one and wear one that actually helps, not just you, but everyone.”