Fixit: More efficient filters made to fit nearly every furnace

Q I was told by a serviceman that our furnace can't handle the high-efficiency filters we want to use. We're supposed to use the regular filter and change it every month. That's a pain and expensive to boot. Is that the only solution?

A It depends on what the technician meant by "high-efficiency filters."

The marketplace of furnace filters has changed dramatically recently. For years, all that was available was the standard furnace filter, a 1-inch-thick fiberglass panel that slipped into a slot in the return duct of the furnace. Typically, the panel was pulled yearly -- or when dirty -- and tossed. Its purpose was to filter the air to protect the furnace; it was not meant necessarily to clean the air for the house's occupants.

Now, there are improved filters offering different levels of filtration. The more filtration, the cleaner and safer the household air as the filter will trap ever smaller particles. It's important to remove small particles from household air, according to the American Lung Association, because they can go deep into the lungs where they cause irritation and decreased lung function. Particulates in the air also can trigger allergic reactions and asthma attacks and increase the incidence of infectious diseases.

But as good as these filters are for a home's occupants, they may not be good for every home. Depending on the design of the furnace and the ductwork in the house, filters with the highest filtration may, in some cases, cause the equipment to overwork and wear out faster. But with at least three levels of filtration available, most furnaces built since the late 1980s can handle some type of improved filter, experts say.

Filter types available include:

• Pleated filters. They are pleated or folded to provide more surface area and better filtration than the standard furnace filter. It is important to change these filters regularly so they do not restrict airflow.

• High Efficiency Particulate Air (HEPA) filters. HEPA filters consist of a core filter that is folded back and forth over corrugated separators that add strength to the core and form the air passages between the pleats. Most homes will need a separate system attached to the furnace to handle these filters.

I'm not sure why the recommendation for your home is to use a standard filter and change it monthly. Ask your technician for an explanation. Also, check your furnace manual for a consumer information number. Call and ask if your furnace can handle the type of filter you are considering.

When shopping for an improved filter:

• Buy the highest efficiency filter that works with your furnace. Look for the MERV (minimum efficiency reporting value) rating on the package. The higher the number, the better.

• Buy a pack of four or six filters to have on hand so you can change the filter when necessary, without delay.