Ozone in small amounts
If all atmospheric ozone were compressed to the pressure at the earth’s surface, the layer would be only 3 mm thick.
Even though ozone occurs in such small quantities it plays a fundamental role for life on earth.

Ozone for better and for worse
The atmosphere surrounding the earth contains small quantities of ozone, most of which is in the ozone layer in the stratosphere, 10-50 km above the earth’s surface.
Stratospheric ozone, together with molecular oxygen, absorbs most of the ultraviolet radiation from the sun. This prevents the radiation from reaching the earths surface where it can damage plants, animals and humans.
The ozone content in the lower layer of air (the troposphere, 0-10 km) has increased through the release of gaseous nitrogen oxides and hydrocarbons from vehicles, industrial plants and other sources. Ozone here can damage crops and people’s health and also contribute to raising the temperature at the surface – the “greenhouse effect”.