Ozone is a triatomic molecule consisting of three oxygen atoms (O3), which occurs naturally in the stratosphere. Ozone can be made artificially in compact electrical units from the oxygen in atmospheric air. Ozone readily gives up one atom of oxygen resulting in a powerful oxidizing agent that is toxic to most waterborne organisms and decays to ordinary oxygen in a few minutes in water.

Ozone is also a very strong, broad spectrum disinfectant that is an effective method to inactivate harmful protozoa and also works well against almost all other pathogens. Ozone is used by many municipal drinking water systems to kill bacteria instead of the more common chlorine because it leaves no residue in the water after treatment. It has the additional advantages of having fewer dangerous by-products and the absence of taste and odour problems associated with chlorination.

Ozone is created in a sealed unit, it is added to the water by bubble contact and is completely safe for users. Units are available that can be fitted to most spas and swimming pools.