Specific effects may include throat irritation, cough, chest pain and shortness of breath, as well as an increased risk of respiratory infections. Some ozone air purifiers are manufactured with an ion generator, sometimes called an ionizer, in the same unit. As mentioned above, ionizers produce ozone. This occurs when negative ions electrically charge particles in the air.
Since the conflicting data associated with the ionizer remains persistent, I usually keep my ionizer option turned off. In their 6-month study, the authors found no statistically significant difference in PEFR between active ionization and placebo or non-ionizer environments. These ionizers turn on for 8 hours every day, and I have a Therapure TPP300D with UV+ ionizer that turns on for 8 hours in my living room. Air ionizers are designed to help provide cleaner air and they do so through the use of ionized particles.
Ionizer air purifiers are generally safe because ionizers aren't energized enough to be harmful to you.