Time for some links to this important subject. Carbon Monoxide has an attraction to the Iron in our blood hemoglobin 200 times stronger than Oxygen. Nitrous Oxide (laughing gas) and Hydrogen Sulfide act the same way when we are exposed to breathing those gasses as well.
Treatment is to get the person to fresh air ASAP. Full Oxygen is the treatment, either by a pressure mask or hyperbolic chamber.
Here's one link. Doo a google search on "CO vs hemoglobin" Make sure you Java is up to date