What are Ozone Depleting Substances?
Ozone Depleting Substances (ODSs) are gases that contain chlorine or bromine atoms in forms able to reach the stratosphere, where they can take part in chemical reactions that destroy ozone on a large scale. The best known are the chloroflourocarbons (CFCs), formerly used extensively in refrigeration, air-conditioning, foam-blowing and as aerosol propellants, and the halons (hydrocarbon gases containing bromine), which were widely used as fire extinguishers. Production of all major ODSs is now regulated by the Montreal Protocol. Most ODSs are made by human activity but some do have natural sources as well, including methyl bromide and methyl chloride.
