Halon's Role in Stratospheric Ozone Depletion

The Halon covered by EPA Rule 40 CFR Part 82, Subpart H contains the chemical element bromine (Br) and also, in the case of Halon 1211 specifically, chlorine (Cl). Br and Cl both contribute to stratospheric ozone destruction. The earth's stratosphere is a layer of the atmosphere that begins between 5 and 11 miles above the earth's surface and extends up to about 30 miles above the earth's surface. Ninety percent of the ozone in the earth's atmosphere is found in the stratosphere. The characteristics of Halon and other human-made chemicals that can deplete ozone (e.g., chlorofluorocarbons, or CFCs) enable them to reach the stratosphere, where they break down and the Cl and Br from them can destroy ozone. Halon is a major source of bromine in the stratosphere.