Many of these original refrigerants are flammable and can cause irritation upon exposure. The search for safer alternatives led to the development of chlorinated fiuorocarbons (CFCs) in the 1930s. These refrigerants enabled the large scale development of the refrigeration and air conditioning units we all utilize today.
Two of the CFCs used successfully as refrigerants were Rl 2 (dichlorodifluoromelhane) and R22 (chlorodifluoromelhane). The former was utilized primarily in refrigeration while the latter worked well in air conditioning. R22s selection was due to its higher efficiency and greater capacity as compared to R 12.
Use of CFCs expanded into propellants for aerosol products, which led to the release of large volumes of this refrigerant into the atmosphere. The excellent stability of CFCs enabled them to rise into the Earths stratosphere and negatively impact the ozone layer. CFCs release chlorine radicals when exposed to ultraviolet light in the stratosphere which react with ozone.
"The issue of ozone depletion caused by the presence in the atmosphere of the previously used long-lived, chlorine-containing molecules gave rise to the Montreal Protocol which mandates the replacement of these ozone-depleting substances. As a result, the CFCs have been eliminated and the phase out of the hydrochlorofluorocarbons (HCFCs) is ongoing. Both of these types of refrigerants contain chlorine which, in these molecules, creates issues with respect to ozone depletion. They have been replaced by the HFCs that do not contain chlorine."