Does an oil furnace burn carbon monoxide or carbon dioxide?

Neither, but it PRODUCES carbon monoxide. Any fuel burning system has the potential to produce different levels of carbon monoxide. It is a good idea to have a qualified technician inspect the oil furnace since they need more attention than any other fuel burning appliance. It is also a great idea to purchase a carbon monoxide detector and install one within 15' from any bedroom or if you have a multi level home purchase one for every level. Illinois has a new law that requires one in every home even if it is all electric but with an attached garage. I hope I answered your question.