The most common ozone depleting substances are chlorofluorocarbons (CFCs) used for refrigeration, air-conditioning, blowing foams, solvents, sterilants and aerosol propellants. When released into the atmosphere these CFCs are broken apart by solar radiation, thus releasing a chlorine atom which reacts with the ozone molecule. The chlorine oxide, formed then,

is unstable and consequently will bond with a single oxygen atom. The by-product of this second reaction will be chlorine and another oxygen molecule:

The resulting chlorine undergoes further reactions, allowing the process to be repeated many times. It is estimated that each chlorine atom can destroy 100.000 ozone molecules before it is removed from the stratosphere.

Destruction of the ozone molecule under the influence of the released chlorine from CFC-12

Besides CFCs, bromine compounds (halons, methyl bromide) can also destroy ozone layer.

• What is the ozone • What is ozone hole • Chemistry and depletion •

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