I just came back from the supermarket, and employees there had a tough time understanding me through my half-face respirator. On the other hand, a few days ago, I was talking with a guy who said he is HAZWOPER certified and used to working in Class A HAZMAT suits (full liquid and vapor tight with SCBA for air). He understood every word I said. It was like chatting with an old friend. If anyone is contemplating CBRNE preparedness, there's a lesson there.