Most stratospheric chlorine comes from man-made compounds called chlorofluorocarbons or CFCs. CFCs, widely used in refrigerators and air conditioners, are quite harmless and non-reactive in the lower atmosphere. Carried slowly upward by the earth's winds, they can survive the 5 year journey to the upper stratosphere. Here, above most of the ozone layer, the sun's ultraviolet radiation breaks down the CFCs into the more reactive chlorine compounds that destroy ozone. Chlorine can react with methane to form hydrogen chloride. Chlorine can also react with ozone forming the radical chlorine monoxide. Chlorine monoxide then combines with the radical nitrogen dioxide to form stable chlorine nitrate. Chlorine nitrate and hydrogen chloride are called reservoir gases for the chlorine radical. These reservoir gases usually contain more than ninety percent of the chlorine in the lower stratosphere.
Video slate image reads, "The Upper Atmosphere Research Satellite Chemical Model Animations Showing Ultraviolet radiation reacting with CFCs releasing chlorine, which react with methane to form hydrogen chloride. Then showing chlorine also react with O3 forming the radical chlorine monoxide. Then showing chlorine monoxide combining with the radical nitrogen dioxide to form stable chlorine nitrate."