[Sharlin]

Dying of oxygen deprivation is actually one of the most peaceful ways to go. You just get drowsy, then pass out. The physical feeling of suffocation is caused by CO2 buildup in the blood, not lack of oxygen. So as long as their CO2 scrubbers worked, they could have just turned off the oxygen valve and drift off to sleep.

[52-6F-62]

Thanks for the clarification. I was thinking of it as closer to holding one's breath/atmosphere leaving. I hadn't thought of it simply being an increase in C02 concentration.

[Doxin]

It's not an increase in CO2 concentration. It's a decrease in O2 concentration. Humans can't actually sense low O2 levels, but instead only high CO2 levels.