The primary distinction between ionized air and ozone is that ozone generators are designed to produce ozone, while ionizers can sometimes generate ozone as a by-product. Ozone, a lung irritant, is created indirectly by ion generators and some other electronic air filters and directly by ozone generators. Although some vendors may claim otherwise, there is no difference between ozone in outdoor smog and ozone produced by these devices. Under certain conditions of use, ion generators and other air purifiers that generate ozone can produce levels of this lung irritant significantly above levels considered hazardous to human health.
The Food and Drug Administration (FDA) has set a limit of 0.05 parts per million ozone for medical devices. Ozone can be used to reduce odors and pollutants in unoccupied spaces, such as removing smoke odors from homes involved in fires; however, the levels needed to achieve this are above those generally believed to be safe for humans. Both systems are used to purify or clean air or water. An ozone generator is a purpose-built apparatus for creating ozone in large quantities.
Air purifiers that produce negative ions are not the same as ozone generators; they do not produce ozone in large quantities to clean the air. Air ionizers are designed to help provide cleaner air and they do so through the use of ionized particles. However, conflicting data associated with the ionizer is still persistent, so it is usually best to keep the ionizer option turned off. In addition, when using an ionizer, it is not necessary to move away from it while breathing air, as ionization is beneficial to our body.
These ionizers should be turned on for 8 hours every day; I have a Therapure TPP300D with UV+ ionizer that turns on for 8 hours in my living room. Air ionizers are generally safe because they are not energized enough to be harmful to you. To get rid of the dangers of second and third hand smoking from my roommate, I now plan to keep my ionizer turned on only for 30-40 minutes when no one is in the room, and then turn off the ionizer before anyone comes in.