Guide to purifier types and technologies

Filters

How they work

A fan pulls air through filters. Portable models usually use high-efficiency particulate air (HEPA) filters and might have ultraviolet (UV) or other technologies; whole-house units use pleated fabric filters and are attached to forced-air systems.

Pros: They trap dust, pollen, and smoke without emitting ozone, which can aggravate asthma and decrease lung function.

Cons: Effectiveness varies considerably. They usually cost more per year in replacement filters and electricity than other types. Portable models tend to be noisy at high speeds, and most do-it-yourself whole-house filters scored Fair at best for smoke removal.

Price

$100 to $800 for portables; $20 to $25 for better do-it-yourself whole-house filters; $100 to $350 for whole-house systems (plus $200 or more for installation).

Available as: Portables and whole-house models.

Electrostatic precipitators

How they work

An electrical charge is applied to the particles drawn into the device. Then the particles are captured on oppositely charged plates.

Pros: They have relatively low operating costs. Some do a fine job of removing dust, pollen, and smoke.

Cons: Most create some ozone. Models with small fans or no fans are ineffective at removing dust and smoke. Those with a fan can be noisy at high speeds. The collection plates need frequent cleaning, so there's more maintenance required than with filter-based units.

Price

$250 to $800 for portables; $400 to $1,150 for professionally installed whole-house models (plus $200 or more for installation).

Available as: Portables and whole-house models.

Ozone generators

How they work

They usually use an electrical discharge to separate oxygen molecules in air into atoms that combine with other oxygen molecules to form ozone.

Pros: They can help after serious contamination from a fire or flood but should be used only by professionals when people and pets aren't home. They're not for routine air cleaning.

Cons: All emit hazardous levels of ozone, which can aggravate asthma and decrease lung function. California has banned the distribution and sale of air purifiers that produce 50 parts per billion or more of ozone, effective October 2010.

We don't recommend these and they're not included in our Ratings (available to subscribers).