Chemistry: The Central Science (13th Edition)

Halons such as $CFCl_{3}$ are photodissociated in stratosphere as follows: $CFCl_{3} + hv → Cl + CFCl_{2}$ $O_{3} + Cl → ClO + O_{2}$ $ClO + O_{3} → Cl + 2O_{2}$ Hence Cl ion is available after every cycle and this reaction can continue for thousands of times.