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Why masks with valves do not slow the spread of COVID-19 (1 of 2): Video Transcript (Including Description of Visuals)

[0:00 – 0:07] We see a callout box with text that reads, "NOTE: This high-speed visualization shows airflow when wearing an N95 mask with and without an exhalation valve. It does NOT show movement of virus particles."
 
[0:08 – 0:31] We see side-by-side images of a man with safety glasses and mask, breathing normally. Above the images are the words, "airflow visualization 30 fps (frames per second). 
 
The left image features an N-95 mask with a valve and is labeled "Unfiltered breath." This image on the left shows air streaming outward from the valve as the man breathes.  
 
Simultaneously, the right image features an N-95 mask without a valve and is labeled "Filtered breath." This image shows a soft plume of air escaping from the mask as the man breathes. 
 
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. Cover smart. Do your part. Slow the spread.

Read the accompanying news story.

Why masks with valves do not slow the spread of COVID-19 (1 of 2)
Why masks with valves do not slow the spread of COVID-19 (1 of 2)
This video, created using a schlieren imaging system, shows airflow dynamics when wearing an N95 mask with an exhalation valve (left) and without an exhalation valve. The valve is designed to allow air to escape unfiltered. 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 https://www.nist.gov/news-events/news/2020/11/new-airflow-videos-show-why-masks-exhalation-valves-do-not-slow-spread. Credit: Matthew Staymates/NIST.
Created November 16, 2020