Ozone is chemically very reactive.
In the upper atmosphere ozone is constantly being formed and broken down through a series of reactions known as the Chapman cycle. These reactions maintain a constant concentration of ozone in the upper atmosphere. Therefore, the layer of ozone in the upper atmosphere acts as a shield reducing the amount of UV energy which reaches the earth's surface. UV energy damages the DNA within cells. They have been used in refrigerators, air conditioners, and freezers, as propellants in aerosol sprays, as foaming agents in the production of styrofoam, and as solvents.