Question

What are the main refrigerants used and how do they cause ozone deplation?

Answer 1

The main refrigerants used are Freon chlorofluorocarbons (CFC). They deplete ozone layer.
The chlorofluorocarbons are decomposed by ultraviolet rays to highly reactive chlorine which is produced in the atomic form.
CF₂CI₂ (g)  CF₂CI(g) + (g)
                                       free radical
The free radical [Cl] reacts with ozone and chlorine monoxide is formed.
Cl(g) + O₃(g) → ClO(g) + O₂(g)
This causes depletion of ozone layer and chlorine monoxide so formed reacts with atomic oxygen and produces more chlorine free radicals.
ClO + O → Cl + O₂
Again this free radical destroys ozone and the process  continues thereby giving rise to ozone depletion.