Great article a friend (I forget who, sorry, lemme know if you want credit) posted. Science, facts, etc., on why I'll continue to wear a mask on public mass transport. If I get confronted by some twit, I'll ask just a couple questions before I allow them to continue:
1) How big is the COVID-19 virus particle? (just under 0.1 micrometer)
2) How big are the aerosols and droplets in the air, that the particles get transported on - like when somebody coughs or sneezes, and that stuff hangs around for a bit? (Depending on who you ask, an aerosol is 3 or 5 microns. Particles (that can float in the air, anyway) are 5-30 microns.
3) What's the smallest particle an N95/KN95 mask can filter? (0.3 microns is the usual measure - same for HEPA filters)
This is the part where the mouth breather (ahem) says "Well, if the particle is only 0.1 micron, and the mask lets anything smaller than 0.3 micron through, THEN MASKS DON'T WORK."
Wrong. When you start getting REALLY small (with apologies to Steve Martin), the universe ... changes. People are used to thinking that it's like marbles through a screen - if the screen holes are too big, the marbles eventually get through. A better (if still imperfect) visualization is that if you dump enough marbles on the screen fast enough, they will tend to "clump", block holes, form bigger clumps, and have their progress impeded and possibly eventually eliminated.
An even better visualization is, instead of marbles, think ball bearings, bigger than the screen squares ... these are particles/aerosols. The virus is magnetic BB's, attracted to both the screen and the ball bearings. Some will stick to the screen itself - a LOT will stick (are already stuck) to the ball bearings even before they hit the screen.