From Glossary of Meteorology
A colorless, odorless, very toxic gas; formula CO, molecular weight 28.
It is an intermediate product in the oxidation or combustion of organic material. It is present in the atmosphere at varying levels but is found everywhere, a result of its widely distributed sources and fairly long lifetime. Carbon monoxide is oxidized to carbon dioxide by the hydroxyl radical (OH) and plays a part in local and regional air quality.