Natural gas does not automatically produce CO. This only happens when there is a problem with combustion air, proper draft or both. It's only when natural gas burns incompletely that it becomes a problem. From Natural Gas.Org: When we say that methane is combustible, it means that it is possible to burn it. Chemically, this process consists of a reaction between methane and oxygen. When this reaction takes place, the result is carbon dioxide (CO2), water (H2O), and a great deal of energy. Chemists would write the following to represent the combustion of methane: CH4[g] + 2 O2[g] -> CO2[g] + 2 H2O[l] + 891 kJ Source: Duke Energy Gas Transmission Canada That is, one molecule of methane (the [g] referred to above means it is gaseous form) combined with two oxygen atoms, react to form a carbon dioxide molecule, two water molecules (the [l] above means that the water molecules are in liquid form, although it is usually evaporated during the reaction to give off steam) and 891 kilajoules (kJ) of energy. Natural gas is the cleanest burning fossil fuel. Coal and oil, the other fossil fuels, are more chemically complicated than natural gas, and when combusted, they release a variety of potentially harmful chemicals into the air. Burning methane releases only carbon dioxide and water. Since natural gas is mostly methane, the combustion of natural gas releases fewer byproducts than other fossil fuels.id="maroon"> I have a pdf that talks about it as well, I'll see if I can scrape it up.