Types of Air Purifiers

Four basic types of air purifiers

There are four main types of console-type air purifiers on the market right now. Many air cleaners use combinations of techniques.

HEPA air purifiers. These air cleaners use pleated High Efficiency Particle Arresting (HEPA) filters to trap particles, along with a fan to pull air through the filter. By a wide margin, reviewers say this type of air purifier is the most effective. These models don't produce any ozone at all. Because they use fans, they can be noisy, but some are quieter than others.

Electronic ionizers. This type of air cleaner uses an electronic process to reverse the charge of particles in the air. The charged particles are then attracted to collection plates in the air purifier, as well as to objects in the room -- such as clothing, walls, floors and furniture. In effect, particles are removed from the air and deposited on your furnishings and clothing. To actually remove them from the room, you need to dust and vacuum to prevent allergens from being reintroduced into the air. The Friedrich C-90B is this type of unit, but it also uses a powerful fan and a HEPA filter. Electronic and electrostatic air purifiers produce a small amount of ozone, as discussed above.

UV purifiers. These devices rely on ultraviolet light to neutralize biological contaminants. Experts agree that UV light is effective in destroying microbes such as bacteria, dust mites and mold spores, given sufficient exposure time. According to the Federal Trade Commission, however, most home air purifiers fall short: "Bacterial spores would require a relatively long time under the light for the light to have a killing effect. Most household air cleaners move air too quickly to provide adequate exposure time. "Without the addition of a filter and fan, UV purifiers are ineffective against particles such as dust, pollen and pet dander, and some experts have raised concerns about the safety of UV units in household settings.

Ozone generators. Some air purifiers do nothing but produce large amounts of ozone. These units do not remove allergens from the air since ozone alone has absolutely no effect on particulate allergens. Ozone in large amounts can neutralize strong odors (such as the smoke odor from fire damage), but according to the EPA, this is dangerous for human health. These air purifiers get around the FDA limits for ozone production by not claiming to be medical devices. As discussed earlier, these types of air purifiers have now been banned in the state of California by the state's Air Resources Board. This regulation is the first of its kind in the United States.