Carbon monoxide (CO) is a '''colourless, odourless, poisonous gas''' weighing lighter than air, which is the result of the incomplete combustion of hydrocarbon fuels. It is produced in '''fires, from generators and from car exhaust systems'''. | Carbon monoxide (CO) is a '''colourless, odourless, poisonous gas''' weighing lighter than air, which is the result of the incomplete combustion of hydrocarbon fuels. It is produced in '''fires, from generators and from car exhaust systems'''. |