Electronic air cleaners use a variety of mechanisms to clean the air, including physical filters, ionization and ozone generation. Forced-air units draw room air through a physical filter to trap contaminants, while ionizers and ozone generators rely on the behavior of particles to remove contaminants from the air and room.
One of the most common types of filters used in air cleaners is the HEPA filter. This filter is usually rated to remove 99.97 percent of contaminants larger than 0.3 microns in size and is very effective in reducing pollen, dust and animal dander in a room's air. The filter is sometimes paired with an activated charcoal filter that serves as a pre-filter and also deodorize the air that passes through the unit.
An ionizer charges particles in the air that attract dust, pollen and other physical contaminants. This causes the allergens to become attracted to one another, clumping and falling out of the air column or sticking to surfaces in the room. While this may take the particles out of the air stream, unless they are vacuumed away, they remain present.
Ozone generators create unstable ozone molecules with extra oxygen atoms that react with contaminants, destroying micro-organisms. These devices can be useful for decontaminating rooms and destroying bacteria, but the concentrations of ozone needed to perform this task can be hazardous to human health. Most commercial ozone generators cannot produce antimicrobial results and are more likely to generate respiratory issues than noticeably clean the air.