Researchers studied 14 types of masks to see which offered the most protection — and found that neck fleeces might actually make things worse

Inyoung Choi
Aug 9, 2020,

Ross Chastain wearing a neck fleece while waiting on the grid before the NASCAR Xfinity Series Shady Rays 200 at Kentucky Speedway on July 9 in Sparta, Kentucky. Jared C. Tilton/Getty Images

Researchers at Duke University studied the efficacy of face masks ranging from surgical masks to homemade alternatives like cotton masks, neck fleeces, and bandanas.

The researchers found that while some of the homemade alternative masks offered similar levels of protection from viral particles as surgical masks, neck fleeces and bandanas provided little protection.

They said that wearing a neck fleece actually led to more respiratory droplets than not wearing a mask at all, which "might be counterproductive."

New research by a group of scholars at Duke University compared 14 types of masks to see which would be the most effective at reducing the spread of the coronavirus.

One of them, they found, effectively made things worse.

The researchers tested how effective each mask was at reducing the number of respiratory droplets transmitted during speech — the kinds likely to carry viral particles.

They tested surgical masks, N95 masks, cotton masks, and polypropylene masks, as well as homemade alternatives such as neck fleeces and bandanas. The study involved a test group of people speaking 10 times while wearing each of these masks and a control group of people not wearing any masks.

The researchers found that most of the masks reduced the number of respiratory droplets transmitted compared with the control group, adding to the body of evidence that masks are important in helping to limit the spread of the coronavirus. They found that polypropylene masks transmitted a similar number of droplets as surgical and N95 masks, which transmitted the fewest droplets.

The neck fleece and bandanas, however, had higher counts of respiratory droplets. In fact, the researchers found that the neck fleece increased the number of respiratory droplets by creating several smaller droplets from larger ones, resulting in more droplets than not wearing masks at all.

The study said that since smaller droplets can stay in the air longer than larger droplets, a neck fleece "might be counterproductive."

"We were extremely surprised to find that the number of particles measured with the fleece actually exceeded the number of particles measured without wearing any mask," Martin Fischer, one of the study's authors, told CNN. "We want to emphasize that we really encourage people to wear masks, but we want them to wear masks that actually work."