An electronic air purifier is one which uses electrostatic attraction to trap polluting particles and thereby remove them from the airflow. This is in contrast to mechanical air cleaners, which use filters such as HEPA filters to capture particles.
There are two different types of electronic air purifiers, which use different processes to achieve this same end. The first type is the electrostatic precipitators; the second is the ionizer, also called the ion generator (although, somewhat confusingly, both types of cleaner use ions). The differences between the two will be discussed below.
Both types of electronic air purifiers give an electric charge to the polluting particles. Charged particles, or ions, are by nature attracted to other particles with the opposite charge. The end result is that charged particles will be drawn to and then stick to each other.
Electrostatic precipitators and ionizers differ from each other in how they charge the particles and what happens to the particles after they have been charged.
According to the United States Environmental Protection Agency's guide to air cleaning devices, "Electronic air cleaners exhibit high initial efficiencies in cleaning air, largely because of their ability to remove fine particles." However, the EPA also states that the continued effectiveness of an electrostatic precipitators is highly dependent on keeping the collecting plates clean. The owner of an electrostatic precipitator, therefore, should take care not to forget about this task.
Unless they also include some other mechanism as well, electronic air cleaners (of either type) target only particles, not gasses. This means that many common types of indoor air pollution, such as Volatile Organic Compounds, are not affected by them.
Some electronic purifiers have been known to release ozone into the air, sometimes as a byproduct and sometimes intentionally. Ozone is a pollutant that can cause serious health problems to those who are exposed even to fairly small levels. The dangers of ozone-generating air purifiers have become more widely understood in recent years, however, and as a result many companies have produced electronic air cleaners that do not emit ozone, and their marketing usually prominently reflects that fact. Those shopping for an air purifier are strongly advised to make sure they are not buying an ozone generator, because such devices may well only make their air quality worse.
As indicated above, ion generators, unlike electrostatic precipitators, have no means of collecting pollutants inside the purifier itself. Instead, the particles settle elsewhere in the home, so that air pollution is reduced, but surfaces become dirtier. Some might not consider this a trade-off worth making.
Electronic air purifiers, like their mechanical cousins, focus on removing unwanted particles from the air. They do so using not filters, but electric charges. There are two types of electronic air cleaners: electrostatic precipitators and ionizers. The former have the advantage of collecting pollutants on special plates, whereas the latter simply cause the pollutions to stick to surfaces in your home. Precipitators, however, require regular maintenance or else they will lose their effectiveness.
Perhaps the most important thing to keep in mind if you plan to buy an electronic air cleaner is to make sure it does not produce ozone.