Masks actually have kind of a funny response curve (see 5th page of linked PDF). The masks are basically made out of layers of tiny (as small as 1um) fibres th

Masks actually have kind of a funny response curve (see 5th page of linked PDF). The masks are basically made out of layers of tiny (as small as 1um) fibres that force the air to weave through them to get to you. Larger particles tend to hit fibres on their way through, while smaller ones tend to get pushed out of the way of bigger things like air molecules rushing through and get bumped into the fibres and captured. The things that get though are the ones in the sweet spot of being small enough to make their way around the fibres in the air, but large enough to not simply be knocked out of the path by the air molecules themselves. The lowest efficiency is around 0.04-0.1um on the models tested (so perfect range for most viruses) but even then they were still only dropping to like 94% effectiveness. I expect “94% effective” is still enough to see a significant different but that’s just my gut feeling. All kind of moot, though, as coronaviruses (per 4th page of linked PDF) are actually closer to 0.125um, which is veering back to 100% effectiveness. And if we expect that a lot of transmission is happening in droplets, those are much larger and easily caught by the filter. https://multimedia.3m.com/mws/media/409903O/respiratory-protection-against-biohazards.pdf https://multimedia.3m.com/mws/media/409903O/respiratory-prot...