First post of my GA career for those noticing my handshake status. Question: I see peer reviewed and published evidence that masks do NOT work, but has anyone seen the same saying that they do work? I want to be able to say to my boss that there is no such evidence--I have not found any. You?
Edit: Thanks to everyone for comments and links. Looks like this topic has been discussed in the past (like so many items on this site). I appreciate the input and your patience. Being new, this was good to see.
In terms of filtration, N95 (The best of the masks people wear) means that it stops 95% of particles at 0.3 microns. Far larger than any viral material. Also assumes that the mask is perfectly sealed to the wearer's face, which is rare at best.
In order to protect cross-contamination in a hospital setting, what's most common is a HEPA filter that stops 99.97% of 0.3 microns. So, because they can't guarantee that it will block any contaminants they will typically ALSO have duct mounted UV lights to kill off anything that might slip through.
As far as PPE, like with virologists who actually work with viruses, the only guarantee is through a Self-Contained Breathing Apparatus with an air supply, typically over-pressure so if any leaks occur the clean air blows out rather than contaminated air leaking in.