Another fun fact: the body's suffocation response isn't caused by lack of oxygen. It's caused by high CO2 levels in the blood [0]. If your car floods the air with CO2, you will respond like someone is holding your head under water.

Carbon monoxide kills you by binding more strongly to the hemoglobin than the O2. You don't notice, because the CO2 removal mechanism continues to work fine. You'll usually die before realising anything is wrong.

I just read this fact in Hail Mary, but it doesn’t fully add up to me. If you fall flat on your back and wind yourself (phrenospasm) that triggers an immediate suffocation response which has nothing to do with CO2 and seemingly everything to do with a lack of oxygen.