What is it about?

It was found that wearing masks reduces cough dispersal by reducing exit velocity from the mask with a predictable decrease in velocity. N95 masks were best (0.1-0.25 meter) A 3 ply surgical mask decreased it to 0.5-1.5 meters whereas an uncovered face allowed cough dispersal out to 3 meters. The flow dispersal was related to formation of vortex rings that help it spread.Various methods of covering the face were analyzed and it was found that coughing on an uncovered elbow is not useful and coughing over a covered sleeve or with multiple folded handkerchief through amask were better.

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Why is it important?

The study provides evidence that masks decrease spread of various pathogens independent of filtration capacity by reducing the velocity of coughs in a predictable manner. The study also showed that coughing over an uncovered sleeve can work but not over an uncovered elbow. Other methods(except over a multiple folded handkerchief) also had significant leaks


This study shows that there is a contamination bubble out to 3 meters around a person. Masks reduce this contamination bubble . Intersection of different peoples contamination bubble allows pathogen transmission. Reducing the contamination bubble allows people to move around avoiding transmission. Depending on the people proximity better quality masks may be required. So a combination of mask wearing and appropriate social/physical distancing are required to prevent airborne/droplet disease transmission

Prasanna Simha Mohan Rao
Sri Jayadeva Institute of Cardiovascular Sciences and Research

Read the Original

This page is a summary of: Universal trends in human cough airflows at large distances, Physics of Fluids, August 2020, American Institute of Physics, DOI: 10.1063/5.0021666.
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