[trentdk]

The idea is to stop the respiratory droplets that contain viruses. Droplets measure on the order of micrometers, which is the range that surgical masks are made to be effective.

A Google search result for droplet sizes: https://www.pnas.org/content/115/10/E2386

A Google search result for effectiveness of various masks related to particle size: https://blogs.cdc.gov/niosh-science-blog/2009/10/14/n95/