Chlorofluorocarbons (CFCs) are organic chemical compounds that contain carbon, fluorine, and chlorine atoms. Each CFC is identified by a unique numbering system that describes its structure. The digit in the hundredths place represents the number of carbon atoms in each molecule minus 1, the digit in the tenths place represents the number of hydrogen atoms in each molecule plus 1, and the digit in the units place indicates the number of fluorine atoms. For example, trichlorotrifluoroethane is a CFC that has three fluorine atoms, no hydrogen atoms, and two carbon atoms in each molecule, whence the designation CFC-113, while dichlorodifluoromethane (CFC-12) has one carbon, no hydrogen, and two fluorines.

CFCs are anthropogenic substances and have no natural background level. At room temperature, they are generally volatile, ...