Causes

Carbon monoxide poisoning is caused by inhaling combustion fumes. When too much carbon monoxide is in the air you're breathing, your body replaces the oxygen in your red blood cells with carbon monoxide. This prevents oxygen from reaching your tissues and organs.

Various fuel-burning appliances and engines produce carbon monoxide. The amount of carbon monoxide produced by these sources usually isn't cause for concern. But if they're used in a closed or partially closed space — cooking with a charcoal grill indoors, for example — the carbon monoxide can build to dangerous levels.

Smoke inhalation during a fire also can cause carbon monoxide poisoning.