Gases covered under the 1987 Montreal Protocol, used for refrigeration, air conditioning, packaging, insulation, solvents or aerosol propellants. Since they are not destroyed in the lower atmosphere, CFCs drift into the upper atmosphere where, given suitable conditions, they break down the ozone layer. CFCs are greenhouse gases and considered ozone depleting substances (ODSs). As such, they are being replaced by other compounds: hydrochlorofluorocarbons, an interim replacement for CFCs that are also covered under the Montreal Protocol, and hydrofluorocarbons (weak ODSs), which are covered under the Kyoto Protocol