Whole-house air cleaners.(Clearing The Air)(Evaluation)

Cleaner air is relatively easy to come by in homes with a forced-air central heating or cooling system: Simply replace the panel-style filter in the return duct with one that filters more finely. Most drop into place and allow the system to deliver cleaner air throughout the house. One $15 model we tested, the 3M Filtrete Ultra Allergen Reduction 1250, was especially good at trapping dust. You can also buy whole-house air cleaners that use the electronic-precipitator technology found in the best portables.

At about $400 to $500, whole-house electronic air cleaners cost roughly the same as the best room versions and deliver similar cleaning performance for the whole house. Free-flowing collection systems help them trap more of the smallest, most irritating particles without restricting airflow as some panel-style filters do. But you will have to pay $200 or so for the professional installation electronic models require.

THE TESTS, THE RESULTS

We tested 13 whole-house air filters you can install yourself, along with five models that require professional installation. Three of those five use an electronic precipitator to trap airborne particles, while another--an extended-media filter--relies on a thick ruffle of pleated fabric. The Aprilaire 5000 combines both technologies.

All were tested in the 200-square-foot sealed chamber we used for portable units, but with ductwork to simulate a room in a home with forced-air heating or cooling. Most tested models measure 20x20 inches, but our results should apply to other sizes.

Four pricey performers--and one that's overpriced. All four electronic models were 30 times more effective overall than conventional fiberglass furnace filters. As with room air cleaners, these whole-house versions were especially adept at trapping the smallest particles.

By contrast, the $275 Aprilaire 2200, with its extended-media filter, removed smoke particles no better than the best $8-to-$15 panel filters. Like those, it was some 10 to 15 times as effective on dust as a conventional furnace filter, however.