Thanks for this!

My wife and I have been utter hermits, only visiting with friends masked up, distanced, and outdoors. When I got a sniffle a few weeks ago, I was sure I'd slipped up somehow.

FWIW, the cold was much milder than any I'd experienced before (just a sniffle, and some coughing - but no sore throat or fever). Inspired by your article I did a bit of web searching on viral particle sizes:

A rhinovirus particle is about 0.0003µm, coronavirus is 125µm. N95 masks are effective down to 0.3µm or 100 times larger than a rhinovirus but about four times the size of a coronavirus. So like a chain link fence not stopping sand but blocking tennis balls just fine.

When in an inside space, I wear a P100 respirator (same particle size as N95, but removes 99.96% instead of 95%). A 3M N95 mask might do a better job removing rhinoviruses as the 3M does its work through electrostatic attraction but a respirator is essentially a HEPA filter worn on the face.

Anyway, I am not doing all this to avoid a simple cold - just Covid as an old guy (tm) I'm in a high risk group.

BTW/FWIW, for anyone else wearing a respirator for pollen, pollen ranges from 10-1000µm but, sadly for anyone dealing with wood smoke, those particles are mostly under 1µm, well under the 2.5µm HEPA masks deal with. Again, disposable N95s might be better...