Biggest item seems to be large objects not being able to go through small holes.
That and the certification of masks going through rigorous testing by agencies showing 95% effectiveness against certain size airborne particles. Or they can opt for 100% masks for 100%.
You think medical personnel are just paranoid and don’t need PPE?
There’s a mountain of science here but true, there’s not many willing to go through a Covid trial without masks to prove masks are/not effective. I think they’ll take the agencies decades of testing at face value for particle filtration.