Carbon Monoxide Poisoning Carbon Monoxide Poisoning Carbon monoxide (CO) poisoning is a potentially fatal condition caused by breathing carbon monoxide, which is a colorless and odorless gas produced by the incomplete burning of natural gas, propane, gasoline, kerosene, coal, wood, smoking tobacco, other plant matter, or any other fuel containing carbon. It can also result from breathing the vapors of methylene chloride, a chemical found in paint thinners, degreasers, and solvents