A Guide to Air Filters

Armed with a little knowledge, you can find a filter that helps to create a healthier, cleaner indoor environment for you and your loved ones.

| September/October 2001

  • CARE 2000 portable room filter CWR Environmental Products
  • Particulate filters are the best way to trap pollen and other allergens.
  • Electronic particulate filters can scrub up to 95 percent of dust, dirt, and smoke from a room.
  • Electronic particulate filters can scrub up to 95 percent of dust, dirt, and smoke from a room.

According to John and Lynn Bower, founders of the Healthy House Institute, virtually every home in the country is plagued by indoor air pollution ranging from mild to severe. Filtration is an effective solution, but only after preventive measures are taken to eliminate as much indoor air pollution as possible. Although the American Lung Association and the Environmental Protection Agency recommend air filtration, they say that controlling allergy-causing pollution sources and ventilation are more important. Once these options are exhausted, it is time to think about air filtration.

Portable and Whole-House Filters

While there are many models of air filters, only two basic types of filtration systems exist: portable and whole-house. Portable filters cost between $80 and $500. Whole-house filters cost as little as $1 and as much as $1,000 (including installation).

Portable filters purify the air in a ­single room, and work best when run continuously in a room that is closed off from the rest of the house. Here’s the rub: If you have to seal off a room, portable filters won’t be of much value during the heating and cooling season.

Whole-house filters are designed to clean air in an entire house. One of the easiest and cheapest ways to install a whole-house filter is to insert a filter or several filters into the duct system or onto the heat registers of a forced-air heating system or a central air-conditioning system. Air circulating through the system passes through the filters, which remove impurities. For the system to work optimally, the fan must run at least several hours each day. In addition, you will need a special air filter designed to trap gases and/or particles. Ordinary furnace and air conditioner filters are insufficient, as they’re typically designed to remove only very large particles.

Even better is an air-filtration unit installed in a whole-house mechanical ventilation system. Ventilation systems are rare in older homes but can be installed, albeit for a hefty sum. In houses equipped with a ventilation system that works in conjunction with a forced-air heating/ central air-conditioning system, a single air filter can do double duty. If properly placed, this filter can cleanse fresh air entering the house through the ventilation system and help remove pollutants from air circulating through the heating and/or central air-conditioning system.

Particulate Filters

Whole-house air filtration systems are the most effective, but what kind of filter is best? Particulate filters physically trap suspended particles such as mold, pollen, dust, dander, bacteria, and soot from tobacco smoke or combustion sources such as fireplaces and furnaces. Particulate filters come in three basic types, ranging from $1 to $15. The most commonly used filters contain fiberglass or other synthetic fibrous materials. Some models contain a permanently charged plastic film or fiber material that removes particulates from air passing through the filter. Finally, there’s the panel filter, containing a pleated fabric material. All of these remove about 10 to 40 percent of the large particulates from room air and must be replaced every month or so.

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