Dear Jim: I am having a new furnace and air-conditioning system installed. The contractor is recommending an air cleaner instead of just the standard filter. Is installing one worth the extra cost and which are best? – Bob J.

Dear Bob: The answer to your first question depends upon your particular family and its clean-air needs. Installing an air cleaner on your furnace will improve indoor air quality. If your family has allergy problems or an activity in your home generates much dust, then the extra cost is justified.

Installing an air cleaner also can maintain the highest efficiency level for your heating-cooling system. All air cleaners are mounted on the return air side, so they remove the dirt from the air before it enters the blower.

Clean air reduces the dirt deposits on the heat exchanger surfaces so heat is transferred more efficiently. This is most important when air-conditioning because the cooling coils get damp and the particles stick and build up.

If you don’t install an air cleaner, be careful about installing so-called “air cleaner filters” which slide into the 1-inch filter slot. They are inexpensive and are better than a filter, but they may increase the air flow resistance above the furnace manufacturer’s recommendations as they get dirty. This can reduce the air flow and furnace-air conditioner efficiency.

There really is not one best air cleaner for all needs. Most are effective for larger particles, and others are better at removing finer particles such as smoke. The basic types to consider are electronic, pleated media and self-charging electrostatic.

With any of the above air cleaners, you may consider installing an ultraviolet (UV) light air purifier. The intense UV rays generated inside the air duct kill many bacteria and viruses. This is harmless to people because the light source is totally enclosed in the duct. A UV purifier does not remove particles from the air.

Electronic air cleaners are effective for removing even the smallest particles, and they consume little electricity. The elements slide out for easy cleaning in a dishwasher, and they do not create much air flow resistance. I prefer this type and use one in my own home.

Pleated media models use a thick element to mechanically clean the air. They are very effective for larger particles (mold, pollen, dander) which often cause allergies. Replace the element regularly so the air flow does not become restricted.

Self-charging electrostatic models are the least expensive and slide into the standard filter slot. These clean the air by creating a natural static charge so dirt particles stick in them. Rinse them off once a month with a garden hose or in the bathtub to release the dirt particles.

The following companies offer whole-house air cleaners: Aprilaire (608-257-8801, www

.aprilaire.com), Dust Free (800-441-1107, www.dustfree.com), Home Health Products (866-765-1587, www.airhealth.com), Lakeair International (800-558-9436, www.lakeair.com) and Trion (800-884-0002, www

.trioninc.com).

Send inquiries to James Dulley, 6906 Royalgreen Drive, Cincinnati, Ohio 45244, or visit www.dulley.com.