Stable liquids or gases usually produced for solvents, aerosol propellants, refrigeration, air conditioner or styrofoam purposes. These high vapour pressure liquids/gases are chemically stable and have long atmospheric lifetimes; therefore, they can eventually become well-mixed in the troposphere and ultimately diffuse into the stratosphere. Upon encountering high energy UV light in the upper stratosphere these species are photodissociated and ultimately release all of their atoms there. The free radical chlorines (or bromines in the case of some halons) catalytically destroy ozone (see chlorine) in the stratosphere.