Translations:Adventist Youth Honors Answer Book/Health and Science/Chemistry/49/en

Oxygen is carried to the cells from the lungs by red blood cells and CO₂ is carried back to the lungs to be breathed out. Red blood cells have a 3-D space that fits oxygen and CO₂ but allows them to be ejected when they reach their destination. CO can also fit the space but won't let go, so a red blood cell that has CO loaded is no longer available to do its job. If enough red blood cells are affected, the body cells cannot get the oxygen they need and waste CO₂ builds up, leading to death.