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Why masks with valves do not slow the spread of COVID-19 (2 of 2): Video Transcript (Including Description of Visuals)

[0:00 – 0:10] We see side-by-side images of three mannequins in front of a black background. Above the image are the words, "Light scattering technique 125 fps." 
 
The left mannequin is labeled "Unfiltered breath" and is wearing a mask with a valve; when it expels air, we see a white plume directed downward from the valve. 
 
The center mannequin is labeled "Filtered breath" and is wearing an N-95 mask without a valve; when it expels air, the only visible indication are some white wisps where the neck and mask meets.  
 
The right mannequin is labeled "Unfiltered breath" and features the mannequin without any mask; when it expels air, we see a white plume of air exiting the mouth and leaving the screen.  
 
Text reads, "The CDC recommends that people wear masks in the public to slow the spread of COVID-19.  However, masks with exhalation valves allow exhaled breath to escape unfiltered. 
 
[0:10 – 0:20] Visualization repeats. Text reads, "Cover smart. Do your part. Slow the spread."

Read the accompanying news article.

Why masks with valves do not slow the spread of COVID-19 (2 of 2)
Why masks with valves do not slow the spread of COVID-19 (2 of 2)
This video, created using a light scattering technique, shows airflow dynamics when wearing an N95 mask with an exhalation valve (left) and without an exhalation valve (center). Masks with valves do not slow the spread of COVID and should not be worn for that purpose, according to the CDC. Read more about this video https://www.nist.gov/news-events/news/2020/11/new-airflow-videos-show-w…. Credit: Matthew Staymates/NIST.
Created November 16, 2020