he main reason of ozone layer depletion is belived to be the release of chlorofluorocarbon compounds ($CFCs$), also known as freons. These compounds are nonreaction non-flammable, non toxic organic molecules.

These are used in refrigerators, air conditioners in the production of plastic foam and by the electronic industry for cleaing computer parts.

$CFCs$ are released in the atmosphere, they mix with the normal atmospheric gases and eventually reach the stratosphere. In stratosphere, they get broken down by powerful $UV$ radiations, releasing chlorine free radical.

$\mathrm{CF}_{2} \mathrm{Cl}_{2(\mathrm{~g})} \stackrel{\mathrm{UV}}{\longrightarrow} \dot{\mathrm{Cl}}_{(\mathrm{g})}+\dot{\mathrm{C} \mathrm{F}_{2} \mathrm{Cl}_{(\mathrm{g})}} \ldots \ldots$ $(i)$

The chlorine radical then react with stratospheric ozone to form chlorine monoxide radicals and molecular oxygen.

$\mathrm{Cl}_{(\mathrm{g})}+\mathrm{O}_{3(\mathrm{~g})} \rightarrow \mathrm{ClO}_{(\mathrm{g})}+\mathrm{O}_{2(\mathrm{~g})} \quad \ldots . . \text { (ii) }$

Reaction of chlorine monoxide radical with atomic oxygen produces more chlorine radicals.

$\mathrm{Cl} \dot{\mathrm{O}}_{(\mathrm{g})}+\mathrm{O}_{(\mathrm{g})} \rightarrow \dot{\mathrm{C}} \mathrm{l}_{(\mathrm{g})}+\mathrm{O}_{2(\mathrm{~g})}$$….(3)$

The chlorine radicals are continuously regenerated and cause the breakdown of ozone. Thus, $CFCs$ are transporting agents for continuously generating chlorine radicals into the stratosphere and damaging the ozone layer.