Basic Carbon Monoxide Facts Carbon monoxide (CO) is an odorless, colorless, tasteless gas that is slightly lighter than air. It is sometimes called carbonic oxide, exhaust gas or flue gas. It becomes a liquid under high pressure. It can also kill within minutes in high concentrations. Where Does Carbon Monoxide Come From? Carbon monoxide is produced by the incomplete combustion of any fuel that contains carbon. This includes gasoline, natural gas, oil and propane, as well as coal and wood products. What Are the Main Sources of Carbon Monoxide? At home, sources of carbon monoxide include gas- and oil-burning appliances such as furnaces, dryers, water heaters, […]