CFC (Chlorofluorocarbon) as "coolants for commercial and home refrigeration units, aerosol propellants, electronic cleaning solvents, and blowing agents" causes ozone depletion.
The reaction that causes ozone depletion is basicly this:
Cl atoms act as a catalyst to speed up the break of O3 into O2.
Cl + O3 → ClO + O2
ClO + O3 → Cl + 2 O2
so you can see that in the reaction above, 1 Cl atom can destroy 2 O3 atoms, and Cl is not consume in the process, which keeps the reaction going.