This video produced by researchers at Bauhaus-Universität Weimar demonstrates the effect on the air surrounding a person when they cough. Starting clockwise at top left, it shows as a baseline the air flow during normal breathing, then while coughing unrestricted, while coughing into the hand, while coughing into the elbow, while coughing into a dust mask, and finally while coughing into a surgical mask.
The contrast in how air is moved between coughing unrestricted and coughing with a surgical mask is dramatic; the former travels forward explosively like a cannon while the latter combusts upwards more like a puff of smoke. Yet it’s still shocking—though I suppose it shouldn’t be—how much the surgical mask does not suppress. The university has more on how they were able to capture this visualization at uni-weimar.de.
Below is a similar visualization from Dr. Lydia Bourouiba at M.I.T. that shows, at 2,000 frames per second, how the micro-droplets of an unrestricted sneeze travel directly in front of a person in a “turbulent gas cloud.” The visual clarity here is even more striking and, though sneezing is not as closely associated with COVID-19 as coughing, still horrifying. The video shows how micro-droplets can continue to spread well beyond the six-foot safety zone we’ve all become acutely aware of in recent weeks. In an accompanying article, Dr. Bourouiba writes:
Peak exhalation speeds can reach up to 33 to 100 feet per second (10-30 m/s), creating a cloud that can span approximately 23 to 27 feet (7-8 m).
It’s worth noting that so much is still not known about COVID-19 so it’s probably not wise to draw conclusions exclusively from these videos about how the coronavirus spreads. Still, if nothing else, these visualizations underscore the importance of social distancing and the value of wearing masks in public.