>>2680
Oh boy The Bear knows better again.
Look here just because you survive some adverse conditions doesn't mean they're good. CO2 levels above 1000 ppm significantly impede your cognitive functions and more than 5000 ppm are a serious health issue in the long run. Apart from that it just feels gross. I hate stale air.

>Blow up a large plastic bag with normal breaths, then rebreath it
Do I look like some glue huffing gypsy to you?