Some air cleaners (called ozone generators) use an electrical charge to generate ozone in an attempt to clean the air. This has been done for more than 100 years.[7] Although ozone can be used in reducing odors and pollutants in unoccupied spaces (such as removing smoke odors from homes involved in fires), the levels needed to do this are much too dangerous to breathe. The levels of ozone produced by ozone generators sold as air cleaners are too low to clean the air and too high to be healthy. Scientific research has shown that low levels of ozone will not remove indoor air contaminants.[7]

Before buying any electronic air cleaner, find out if it has been tested for ozone production. Air cleaners that produce ozone are bad for people who suffer from asthma; for children; for the elderly; or for people with emphysema, bronchitis, or other respiratory diseases. Because of that, the Wisconsin Department of Health and Family Services urged people who have chronic respiratory diseases or compromised immune functions to immediately turn off any ozone-generating machine.[8] Low amounts (above 0.08 ppm) of ozone can cause eye/nose/throat irritation, chest pain, coughing, nausea, throat irritation, and congestion. It may also worsen bronchitis, heart disease, emphysema, and asthma, and can make it harder for the body to fight off respiratory infections. Not only can ozone be toxic to human health, but it can also hurt indoor plants and damage materials such as rubber, electrical wire coatings, and fabrics and artwork containing certain dyes and pigments.

Contrary to the claims of some vendors, no agency of the federal government has approved these devices for use in occupied spaces, and the FDA has set a limit of 0.05 ppm of ozone in indoor air. Even when one follows the manufacturer's instructions, some studies have shown that the ozone concentrations produced by ozone generators can be higher than this 0.05 ppm limit. Because of misleading information being given to people about these machines, the Federal Trade Commission (FTC) has even taken legal action against some manufacturers of ozone generating machines to prohibit them from making unsupported claims about the ability of the machines to clean air or to provide health-related benefits. In 1995, one manufacturer told the FTC they would stop making health claims about their ozone generators, but they continued to make the claims; the FTC sued them in 1997. The case went to court and the manufacturer was found guilty in November 1999 of making unwarranted claims. The manufacturer promised an "intense effort" to modify its sales pitch after that ruling. Within days of the ruling, a representative from that same company sold 11 ozone units to 6 Ohio school districts. Two of these ozone devices were sold to elementary schools after telling them that the machines would help "kill" widespread fungal infestations in their old schools. An injunction was files against them by the FTC in January 2000 to force them again to stop making these claims.[9]