Ok
LINK explains the science, better then I can I think.
However it kind of makes sense if you have ever followed a smoker in the street.
To keep myself grounded, I try and see breath as anyone talking who MAY spit a little while talking.
I don't have to be too far away if they are standing still, to avoid....shop or queue etc..but do if they are puffing away on the push bike in front or jogging ahead of me as I run behind them.
And as for masks.
I did post ages back some Chinese uni tested home made masks at 80%÷ as effective as FFP1
The understanding I got is the filter rate of material is important..I think denser aka harder to breathe through. Think tea towel versus cotton shirt, is better.
I saw and tried the sock mask. Yeah I know
But it was simple, and better then nothing.
I tied mine with elastic through the loops behind my head ( yes I never got out of that blue Peter stage ) and it felt and looked ok. Might be Better then nothing until mask arrives.