[wongarsu]

More like from 0.02% to 0.04%. But at 0.1% people start complaining about drowsiness and at 0.2% you get worse concentration, loss of focus, increased heart rate, etc. Even if it didn't have such bad effects on the environment we live in we should stop pressing down the accelerator.

[card_zero]

Hmm, so like one seventh to one quarter of the way (depending which of us is counting) to feeling perceptibly close and stuffy. Useful context.