Ozone (O₃) is a highly reactive molecule composed of three linked oxygen atoms. It forms a colorless gas with a biting, acrid odor. Ozone is a strong oxidizing agent, meaning that it reacts with and damages vegetation, building materials (such as paint, rubber, and plastics), and sensitive tissues (such as eyes and lungs). Because ozone is a good disinfectant, it can be used to purify water or sterilize surgical instruments. Ozone is created by electric discharges such as lightning or arcing of electrical contacts as well as by high intensity, short wavelength light.

Ozone is a natural component of the atmosphere. It is both formed and destroyed by ultraviolet radiation in a photochemical reaction cycle in which reactive oxygen molecules are alternately added to and removed from ordinary diatomic oxygen molecules. Usually these reactions occur mainly in the stratosphere where the resulting ozone provides an important shield that...