Humidity makes face masks more effective, but there’s a big catch

Brittany A. Roston - Mar 9, 2021, 4:27pm CST
Humidity makes face masks more effective, but there’s a big catch

Wear a face mask for a long enough duration and you’ll notice that it becomes a bit moist on the inside, each breath contributing to an increasingly humid environment. Though somewhat unpleasant, this humid environment makes face masks more effective at filtering the virus behind COVID-19, according to a new study — assuming the mask is made from the correct material.

It’s no secret that everyone should wear face masks to help prevent the spread of COVID-19. These masks work by reducing how far droplets can spread when someone exhales, filtering some of the droplets that may otherwise carry the virus to people nearby.

According to a new study from the National Institute of Standards and Technology, as well as the Museum Conservation Institute at the Smithsonian, humid masks are better able to filter the droplets. The benefit was only found with masks made from cotton, however, with synthetic fabric masks showing poorer performance in comparison.

Likewise, the light blue medical face masks didn’t benefit from humidity caused by breathing, though their overall performance was about the same as the cotton masks. The findings were based on testing conditions that simulated the humidity produced when someone breathes.

Multiple studies have found that tightly woven cotton fabrics are effective at reducing the spread of droplets, particularly if at least two fabric layers are used. This latest study underscores that effectiveness, finding that the natural humidity that results from breathing increases the performance of cotton face masks.


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