The CO2 DOES trigger the breathing reflex, but surely the low O2 level causes the blackout? The brain shuts everything non vital down when the O2 level gets too low, to conserve as much of the remaining O2 as possible. Never read/heard of the blackout being caused by the build up of CO2. I could be wrong, dunno.
But my biggest problem is the buildup of CO2, that breathing reflex is a bitch to fight
