Look up Brownian motion.
Maybe you will understand after you read it
It’s physics.
Of course, if you have a gap then Covid can side step.
Again, you are trying to reduce the viral load...not totally eradicate it. No one is going to walk around in a biohazard suit to the grocery store...well a few have but probably as some stunt.
And masks are fomites.
Not that we eat out anymore, but when we did I was always more worried about hepatitis or noro than any respiratory bug.
I’ve been hearing horror stories of employees in restaurants who wear the same mask into the bathroom and out again.
EUW.