A Good Ozone Link

Sunlight creates new ozone from O₂ by breaking the bond with a UV photon. The liberated O atoms are then free to join with another O₂ atom to for ozone (O₃). Arctic regions, however, go without sunlight for months at a time. During these periods, ozone is destroyed by a cyclic reaction with Chlorine (Cl) atoms that come from chemicals called cholorofluorocarbons, or CFCs, that were used in air conditioners and refrigerators in the U.S., until recently. Each Cl atom can destroy tens to hundreds of thousands of ozone molecules before it is reincorporated into a more inert form.

CFCl3 + UV Light ==> CFCl2 + Cl
Cl + O3 ==> ClO + O2
ClO + O ==> Cl + O2

The free chlorine atom is then free to attack another ozone molecule

Cl + O3 ==> ClO + O2
ClO + O ==> Cl + O2

and again ...

Cl + O3 ==> ClO + O2
ClO + O ==> Cl + O2

and again... for thousands of times.