I was a bit over the normal once, not red, but high, so the guy told me to stand aside and to take my mask off which I did. After a few minutes of free breathing he gunned me again and I was normal.
Shows what a mask can do, as it traps our breath.
Ps. I do the vote upvote thing manually on 10%, as I don't know how to auto-vote it. Correct me if I am wrong.