Unmasking COVID-19: Exhalation Valves DO NOT Slow the Spread

National Institute of Standards and Technology (NIST) research engineer, Matthew Staymates, has recently examined the effectiveness of exhalation valves in stopping the spread of COVID-19. 

Using a schlieren imaging system, Staymates was able to show airflow dynamics of a person wearing an N95 mask with an exhalation valve and without an exhalation valve. With a schlieren imaging system, exhaled breath becomes visible because it is warmer, and therefore less dense, than the surrounding air. Valves are typically placed on masks to allow for easier breathing and allow air to escape unfiltered. However, Staymates' videos show that N95 masks allow air to pass right through.

Staymates also wanted to examine the movement of exhaled droplets since droplets are one major source of spreading COVID. He decided to build an apparatus that emits air the same as a resting human does and connected the device to a mannequin to best simulate actual human breath. An LED light placed behind the mannequin then illuminated the airborne droplets, which scattered the light and allowed them to appear brightly on the camera. He discovered that droplets escaped unfiltered through the valve of an N95 mask. Overall, Staymates' research shows that masks with valves do not slow the spread of COVID and should not be worn for the purpose of stopping the spread.

Staymates was quoted as saying: "I don't wear a mask to protect myself. I wear it to protect my neighbor, because I might be asymptomatic and spread the virus without even knowing it," Staymates said. "But if I'm wearing a mask with a valve on it, I'm not helping."

Matthew received his Bachelor's of Science and Master's of Science degrees in Mechanical Engineering at Penn State University and has had over 25 published research projects. His research interests focus on improved metrology technologies for evaluating trace explosives and narcotics detection technology. He also has great interest in fluid dynamics and particle release mechanisms. He decided to temporarily shift his interests towards mask design to help slow the spread of COVID. He is currently the Explosives Safety Officer for NIST and oversees the safe handling of high explosives and energetic materials. SUPER COOL!

Sources:

https://phys.org/news/2020-11-valves-n95-masks-filter-exhaled.html

https://www.nist.gov/people/matthew-e-staymates