Ozone is a chemical compound consisting of three oxygen atoms (O3). It is a very high energy-carrying form of diatomic normal atmospheric oxygen (O2). Thus, the structures of these two kinds of molecules differ from each other as follows:

O3 is a colorless gas with a characteristic odor at room temperature. (felt after stormy weather, in high places or by the sea). Its name comes from the Greek ozein meaning “to smell”. It was discovered in 1840 by the German chemist Christian Friedrich Schönbein (1799-1868). Near ground levels, one particle per 10 million air particles is present in the form of smoke at concentrations of O3 (= 0.1 ppm = 200 µg/m³). At an altitude of 2000 meters, it decreases much less to 0.03 – 0.04 ppm.

Thanks to its very strong oxidizing and very effective disinfecting properties, it is used as a germicidal in treatment plants that provide drinking water around the world.