Freons are chlorofluorocarbons introduced into the atmosphere from aerosol sprays and refrigerating equipments. They have a very long life time and when they reach stratosphere, they undergo photochemical decomposition and destroy ozone by the following sequence of reactions :
$CF_2 Cl_2 \xrightarrow{hv} CF_2Cl^+ + Cl^+ $
$CFCl_3 \xrightarrow{hv} CFCl_2^+ + Cl^+ $
$ Cl^+ + O_3 \rightarrow ClO^+ +O_2$
$ ClO^+ + O \rightarrow Cl^+ + O_2$