>>33573966
I wouldn't be too sure about that. Carbon monoxide poisoning is simply one more way to deprive the body and brain of oxygen: carbon monoxide binds permanently to the haemoglobin in your blood so that the blood can no longer carry oxygen around the body.
My sister's ex-boyfriend had non-fatal carbon monoxide poisoning for a while thanks to a malfunctioning gas heater, and it made him very sick indeed - he felt like he had flu for weeks. (Which unfortunately led to him staying in with the heater on - he was lucky it was spotted!) And asphyxiation with (say) Nitrogen is something that is banned in many countries as a method of slaughtering animals, because it causes too much suffering. Quite what will be going through your mind while your brain is *slowly* dying from insufficient oxygen over the course of hours or more is anyone's guess, but there's no reason to assume it's pleasant.