Came to say precisely this. Before you run out of o2 the co2 levels will likely render you unconscious, and will potentially also suppress your breathing.
I took a lungful (choked on the first breath, coughed, started really choking) of air heavy with co2 in a pub cellar once. Only because I fainted on top of the kegs above the co2 saturated air on the floor (leaky cylinder valve) am I here to tell you about it. Tastes like acidic metal and black velvet rushes in.
I took a lungful (choked on the first breath, coughed, started really choking) of air heavy with co2 in a pub cellar once. Only because I fainted on top of the kegs above the co2 saturated air on the floor (leaky cylinder valve) am I here to tell you about it. Tastes like acidic metal and black velvet rushes in.