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.
Electrostatic precipitators draw air into the purifier. The polluted air passes through an ionizing mechanism which gives the particles a charge. After this, the now-charged particles continue through to the next section of the purifier, which contains plates that have the charge opposite to the charge just given to the particles (e.g., if the particles are positively charged, the plates are negatively charged). The particles therefore stick to the plates and are removed from the air. The plates must be cleaned periodically or will cease to capture the particles.
Ion generators differ in that, instead of drawing the particles in and then charging them, they release ions into the surrounding air. These ions attach themselves to airborne particles, thereby charging them. The newly charged particles then become attracted to surfaces such as drapes or walls, or they combine with other particles and fall to the floor.
Effectiveness of Electronic Air Cleaners
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.