Why is carbon monoxide dangerous?

Because CO robs your blood of oxygen.
When you inhale carbon monoxide, it bonds with the haemoglobin in your blood, displacing life-giving oxygen. This produces a toxic compound in your blood called “Carboxyhaemoglobin” (COHb). Over time, exposure to CO can make you sick. Victims exposed to enough carbon monoxide can suffer brain damage or even die.

According to the Journal of the American Medical Association (JAMA), 1500 people die each year because of CO poisoning and another 10,000 become ill. Since you can’t see, smell, or taste carbon monoxide, it can make you sick before you even know it’s there.