Earlier quoted context omitted.
In that scenario, as long as they could keep CO2 levels down, running out of oxygen isn't so bad (ignoring the other troubles). The human body can't detect a lack of oxygen, you just get tired and light headed and pass out.
i understand what you are basing your statement on (a cleaner version would be asphyxiation by breathing an inert gas) but you are very wrong. as a matter of fact people with an impaired amygdala who can't experience fear will panic when forced to breathe co2. also your breathing will get very shallow and cause co2 to accumulate triggering those very receptors you argue will stay silent. https://www.nature.com/articl…
Wouldn't that wake them up?
I also assumed that too much CO2 fast is the key not the super slow version of what those people in the sub have experienced