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 harmful to human health. A small percentage of air purifiers claiming a health benefit may be regulated by the FDA as a medical device. If you are wondering about the differences between an air ionizer and the typical HEPA filter on the market, below is a quick comparison table showing the differences between these products. Laboratory tests were conducted with particulate air and gas samples in a large semi-furnished chamber and in a field test with an ionizing device installed in an air handling unit serving an occupied office building.
As more information is disseminated and presented to the public about the dangers of air ionizers, the more informed consumers will be before purchasing an air purifier, and they are likely to be aware of and avoid these potentially hazardous ionizing air systems. Another recent study of air ionizers in school classrooms reduced particle concentrations and led to some improvements in respiratory health among children 11 to 14 years old, ionizers had an adverse effect on heart rate variability (a measure of cardiovascular health), meaning that any benefit to the lungs came at a cost to the heart. Air ionizers are designed to help provide cleaner air and they do so through the use of ionized particles. Chamber and field tests found that an ionizing device led to a decrease in some volatile organic compounds (VOCs), including xylenes, but an increase in others, oxygenated VOCs more prominently (for example, if you have made it this far and digested all the information about air ionizers (already are marketed as an ionic air purifier or ionizer), you've probably already realized that most people shouldn't buy an air purifier with an ionizing function.
Since the conflicting data associated with the ionizer remains persistent, I usually keep my ionizer option turned off. 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. However, 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. Ionizer air purifiers are generally safe because ionizers aren't energized enough to be harmful to you.