Carbonyl chloride is a molecule that contains the functional group -COCl. This compound is also known as phosgene, which is arguably the most widely used name for this molecule. Alternatively, it is also referred to as carbon oxychloride, carbonic dichloride, and chloroformyl chloride. Its IUPAC name is carbonyl dichloride. Phosgene gas was widely used in chemical warfare during World War I, and is still used in industrial processes for the production of various chemical compounds, including methylene diphenyl diisocyanate (MDI) used in the production of polyurethane foam. Despite its widespread use, phosgene gas is highly toxic and exposure to even small concentrations can be life-threatening.