[tzs]

If I have it and you do not, for me to infect you requires that (1) I release viruses, (2) those viruses make their way to you, and (3) enough of them get into you to give you COVID.

The biggest benefit from masks in most public situations comes from reducing #1 and #2, because almost all viruses I'll be releasing in public will be coming out via my mouth and nose in respiratory droplets.

My mask will catch and stop many of those from getting out. Those that do get through the mask will do so with less force than they would have without the mask, which will limit the range of their spread.

On the receiving end, #3, a good mask should reduce the number of viruses that you take in directly through the mouth and nose, but it won't help with the eyes. Your tear ducts connect inside your head to your nasal system, so if you get viral laden droplets in your eyes they can make it in.

If we are both wearing masks, the combination of my mask reducing the number of viruses reaching you, and your mask reducing the number that get in directly through the nose and mouth, leaving only those the get in via other means such as your tear ducts, hopefully reduces in most cases the number you take in to below the infectious load.