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. Most ionic air purifiers (ionizers) are completely safe and not bad for your health. They emit negative ions into the air as a way to clean it, which is harmless to you.
They are often confused with ozone generators that emit high levels of ozone that can be harmful to health. Particles in the air, such as dust, toxins and germs, can cause poor indoor quality. This can affect your breathing and, over time, cause unwanted health effects. It can also worsen existing conditions, such as asthma.
Several studies have shown that air is not purified with safe levels of ozone, since it cannot oxidize air pollutants to this level. Most room ionizers produce hazardous levels of ozone and produce more concentration in the room. However, some room ionizers have built-in controllers to prevent ozone levels from exceeding safe limits. A further concern is that continuous exposure to ozone attenuates the sense of smell.
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. 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, another recent study of air ionizers in school classrooms reduced concentrations of particles, led to some improved respiratory health among children aged 11 to 14 years, ionizers had an adverse effect on heart rate variability (a measure of cardiovascular health), meaning that any benefit to the lungs had a cost to the heart.