Very good proposition. This can happen next to old mines, waste rock piles especially. Not so much that the CO2 kills you, but it displaces the oxygen. You ent

Very good proposition. This can happen next to old mines, waste rock piles especially. Not so much that the CO2 kills you, but it displaces the oxygen. You enter an oxygen deficient environment. Suffocation can happen almost instantly. Similar to confined spaces. However with weather changes, lets say a low pressure system moving in, the CO2 exhales from the surrounding porous rock. You starve for oxygen, almost immediately. And even the oxygen in your body gets sucked out. It has happened before, it took a long time for coroner's to figure out. Mine rescue personnel even get killed, thinking they can hold their breath. Have often wondered why this is isn't presented more to the public, so they can be warned. Avoid hollows, low spots, etc, especially in old mining country. (The reactions in the rock use up the oxygen pricing CO2 - But that's a longer discussion...)