In the presence of NO, ozone is produced as a by-product when CO, CH4, and other hydrocarbons are oxidized by OH. NOx also influences the destruction rate of ozone directly as a catalyst (in the stratosphere) and indirectly as a result of reactions that couple NOx to other reactive species such as the odd hydrogen radicals, OH and HO2, and, in the stratosphere, the halogen free radicals chlorine m