CO is dangerous because you don't need to remove the O2 from a room to be lethal. All the other gases cause asphyxiation by taking the place of oxygen in the a

CO is dangerous because you don't need to remove the O2 from a room to be lethal. All the other gases cause asphyxiation by taking the place of oxygen in the air. So once you leave the room, you'll be fine. CO is dangerous because it takes the place of oxygen in the blood and it has a stronger attraction to hemoglobin than oxygen. So get enough CO in your blood and your organs suffocate, even if you are put in a pure O2 environment right away.