The Dirt on Air Filters

Pollen, dusts and dander are only a few of the irritants that plague allergy sufferers and housekeepers alike. Read about a handful of air filters that could cut down — if not eliminate — these airborne pests.

| February/March 2001

Are home filters a magic bullet in allergy relief, or an expensive sugar pill?

The dilemma is that indoor air pollution can be up to ten times greater than levels found outdoors. Such close proximity to dust mites, pet dander, mold, bacteria and mildew, along with outdoor allergens like grasses, weeds and pollen, can make your refuge nothing but a ruse.

There are three methods that help to control indoor pollution: source control, ventilation and air cleaning. Source control (removing the source of the allergens) is the most cost-effective; unfortunately, not all pollutants can be identified or eliminated. Pet dander, for instance, is one of the most prevalent sources of indoor pollution, but getting rid of Fido is more than most pet owners can bear. Ventilation (bringing outside air inside) helps, but most of us don't live in a climate where leaving the windows open year-round is an option. In addition, leaving the windows open allows outside allergens to enter the house. But cleaning the air with filters, even though it's more costly than the other two methods, is probably the best way to reduce the allergens in your house. Combine all three methods and you'll breathe easier.

Filter Functions

There are three general types of filters: mechanical, ion generators and electronic air cleaners. In addition, there are "hybrid" systems that combine mechanical, ion and/or electronic features.

Mechanical filters are the models found in most homes with central heating and/or air conditioning. They are also found in portable fan-forced units and serve as register covers where an air duct enters a room. The standard mechanical filter is a flat filter that contains coarse fibers (typically fiberglass, aluminum or synthetic material) held in place with a cardboard or plastic frame. Other models use an "electret" media, which is a permanently charged plastic film or fiber. A third type is a panel filter, which has a pleated or an extended surface.

Generally, mechanical filters are efficient at collecting large particles, but remove a small percentage of smaller particles (the panel filter is somewhat more efficient at small-particle capture). With mechanical filters, the more dense the filter material or the greater the filter surface area, the better it will remove pollutants. Whole-house mechanical filters, at $1 to $15 each, are a bargain in the air-cleaner world, but they are also the least effective, stopping only 10% to 40% of pollutants. They also need to be replaced on a monthly or bimonthly basis.

Elizabeth Triano
8/1/2011 4:10:04 PM

Reading about filters, thanks for the info! So, if I have a Sears home central AC unit, with a 30x14x1 pleated filter with a cardboard frame, it sounds like I am better off replacing it with another disposable filter, rather than buying a washable one. The trick is to remember to replace them regularly. Have I got that about right? And I can vacuum it too, to extend life, perhaps?

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