So, if your filter catches the droplets and aerosols, which are much larger in size than the actual virus, the filter works.
And for what it's worth, I'm not anti-mask in the context of the pandemic - I've been wearing masks indoors since the whole thing started and I'll continue to do this until most people around me are vaccinated, for their sake.
anyone with glasses will tell you 1 isn't a very good assumption. As masks saturate in moisture, back pressure causes (1) to be more false.
Human system effects dominate - as the field data shows. It’s like HCQ - works in a lab, not in the real world.
Might be useful in tightly controlled medical settings with adequate filtered ventilation. But there’s no hard evidence beyond that at this stage.
Feynman’s rule still applies.