Thank you for the reply!
1. That's what I thought too, so went to a lot of work to test levels before, during and after breaths. I included results for at the end and beginning of a breath and found that levels JUST BARELY got below the OSHA allowed limit at the end of breathing in.
2. Yes, there is a lot of dead space on normal masks, the that's where the CO2 build up comes from.
3. I have found similar studies, one weirdly also vacuums the air out at the same time, but I'd suggest looking into it if interested and believe what you want. I'm just glad I know finally for myself, thought others might like to know too, and am satisfied :)
