A group of chemicals containing chlorine (Cl), fluorine (F) and carbon (C), sometimes referred to by their trade name Freon. These synthetic compounds were used extensively for refrigeration and aerosol sprays until it was realized that they destroy ozone (they are also very powerful greenhouse gases) and have a very long lifetime once in the atmosphere (more than 100 years). The Montreal Protocol agreement of 1987 has resulted in the scaling down of CFC production and use in industrialised countries.