An ozonizer is a type of air or water purifier which uses ozone to kill bacteria and filter out a wide range of contaminants. Ozone itself is a form of oxygen, though much less stable than the common O2. Ozone is present naturally, mostly in the upper levels of the atmosphere, where it helps deflect ultraviolet radiation. Concentrations of ozone below the atmosphere can be a serious health risk, as ozone is highly toxic to humans and most other forms of life.
An ozonizer is also known as an ozone generator, and is sometimes mistakenly thought of as synonymous to an ionizer or ionic air purifier. An ozonizer does produce ionized particles, and an ionizer does produce trace amounts of ozone, but the two are not the same. An ozonizer creates ozone by charging the air with a burst of high negative voltage. An ionizer works under the same principle, but primarily produces ionized forms of molecules other than ozone.
There are those who claim that an ozonizer may be useful as therapy for a wide range of ailments. Ozone's negative effect on bacteria, fungi and many viruses is thought to help purify the body of these life forms, strengthening the day-to-day functioning of the body. Proponents suggest a range of ozone therapies, including letting the gas into the lungs, injecting ozone directly and drinking ozone-filled water. Detractors point to the toxicity of ozone and hold that any sort of therapy using the relatively high levels of ozone recommended will ultimately be harmful to the patient.
Treatments using an ozonizer are more widely accepted in Asia and parts of Europe than in the United States and much of Western Europe. In China, for example, the use of the ozonizer is wide-spread, and was heavily relied on during the SARS outbreak at the beginning of the 21st century. The medical use of ozonizers is prohibited by the FDA in the United States, though twelve states allow the use of ozone therapy under their alternative medicine statutes -- these states are Alaska, Arizona, Colorado, Georgia, Minnesota, New York, North Carolina, Ohio, Oklahoma, Oregon, South Carolina and Washington State.
In the United States, the ozonizer is most often seen in the context of air purification, where the use of "activated oxygen" is said to help attract dust particles and to kill ambient bacteria and molds. This use as an air purifier is also somewhat debated, as the levels of ozone emitted may or may not be harmful. Ozonizers are also widely used in water purification as an alternative to chlorine. This is particularly true on a small scale, such as for aquariums used to house fish. The ozone kills various algae which otherwise build up in an aquarium environment and can make it an unsuitable habitat for many types of fish.