Answer
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.
Work Step by Step
Given above.
