Story at a glance

  • The study found the neck gaiter material breaks up big particles into many small particles that tend to linger in the air.
  • Researchers said it might be counterproductive to wear such a face covering.
  • N95 masks were unsurprisingly the most effective.

As the number of coronavirus cases topped 20 million worldwide and the U.S. continues to struggle to get a hold on the pandemic, public health experts have largely agreed that wearing masks or face coverings is key to mitigating the spread of the highly transmissible virus as work continues on a vaccine. 


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Anthony Fauci, America’s top infectious disease expert, has for months implored Americans to use masks when out in public, while U.S. Surgeon General Jerome Adams has been pushing people to wear masks, practice social distancing and wash their hands. 

In July, the head of the Centers for Disease Control and Prevention called masks one of the most powerful weapons we have to curb the spread of the virus. The University of Washington’s Institute for Health Metrics and Evaluation even predicts the U.S. could avoid more than 66,000 deaths by the end of the year if 95 percent of Americans wear masks in public. 

But a new study published Friday in the journal Science Advances shows not all masks are created equal, and some may even make things worse. 

Scientists from Duke University came up with a simple test to measure how effective different types of masks were at stopping respiratory droplets from being emitted into the air. Researchers fitted a black box with a laser and a cellphone camera and had testers try out 14 variations of face coverings. 

While wearing the mask, a tester would speak in the direction of the laser inside the box and a camera recorded the amount of respiratory droplets released when someone speaks. Researchers were then able to count how many droplets were released through each type of face covering. 

“We had speakers say ‘stay healthy’ without the mask, and we used that as a baseline,” Martin Fischer, a chemist and physicist at Duke University who developed the experiment, said in a video demonstrating how the study was done. 

“And we then put different masks on and visualize the effects of that mask that should reduce droplet emission when you speak,” he said. 

The study found that the fitted N95 mask worn by health workers was unsurprisingly the most effective, allowing no droplets at all to be released. 

The disposable surgical mask was the second most effective, followed by polypropylene laid in between two layers of cotton. 

Meanwhile, the breathable neck gaiter often worn by runners due to its lightweight polyester spandex material performed the worst. 

It was even worse than the no-mask control group. 

“This one here is fleece, neck fleece, and what’s noticeable here is the number of particles is actually bigger than the no mask case,” Fischer said. 

The researcher said the material of the gaiter breaks up big particles into many small particles that tend to linger in the air. He said it might be counterproductive to wear such a face covering. 

“So it’s not the case that any mask is better than nothing. There are some masks that actually hurt rather than do good,” he said. 

Published on Aug 11, 2020