Chlorofluorocarbons (CFCs) are a class of compounds that contain chlorine, carbon, and fluorine. They are often used in aerosol sprays, refrigerators, blowing agents in the manufacturing of foam, and in air conditioning. CFCs affect the ozone layer of the environment. When CFCs are exposed to ultraviolet radiation in the upper ozone layer, they release chlorine atoms. Ozone is made of three oxygen atoms. When chlorine breaks away from a CFC in the ozone layer, the chlorine replaces an oxygen from an ozone molecule to form chlorine oxide. In this way, CFCs reduce the protection that the ozone layer gives the Earth from the harmful UV rays that are produced form the Sun. CFCs are also thought to be greenhouse gases that contribute to Earth’s global warming.