Dear Jim: Our entire family has various allergies -- headaches, sneezing, itchy eyes, etc. We are considering installing a central air cleaner, but we do not know which type to get. Which ones are most effective? -- Mary R.
Dear Mary: It is easy to get confused when selecting the proper central furnace/air conditioner air cleaner. The prices range from about $25 to more than $1,000 and many of them look similar. The specific model that is best for one family's problems may not be the best for another.
A good air cleaner may also lower your utility bills. By keeping the heat exchangers cleaner, they are more efficient. Also, some poor air cleaners create too much air flow resistance which harms air conditioner efficiency.
The primary air cleaner filtration methods are self-charging electrostatic, electronic, bypass and pleated media. First determine which specific allergens, dust, smoke, etc., that you need to remove. The effectiveness of each of the designs varies depending on the size of allergen.
The self-charging design (I use this type) does not require any sheet metal work on the duct system. These units slip into the typical existing filter slot. Since most common allergens (mold, pollen, dander) are fairly large particles, this air cleaner design is very effective and reasonably priced.
A combination of filter materials is used to create a natural static self-charge. As air flows through, the allergens stick to the filter. Every month or two, slide it out and rinse it in a bathtub. When it is wet, the charge is gone, so dirt and allergens rinse away. Dry it and slip it back in.
Electronic air cleaners operate on a similar concept, but the charge is created with electricity. If you have a problem with cigarette smoke, this design is particularly effective. These must be cleaned regularly or they lose their effectiveness and may create ozone gas from electric arcing.
The bypass design uses a hospital-grade HEPA filter and a large carbon element for odors. It has its own blower to force the air through the HEPA filter element. This is a very effective filter for all allergens, but it is expensive, often requires professional installation and uses electricity.
Pleated media filters work by simply trapping the particles. The better ones are thick and require sheet metal work to install. They are not washable.
When selecting your air cleaner, compare the effectiveness as measured by the dust arrestance rating. The best ones are above 80 percent. Also compare the initial air resistance rating. A lower rating number is better so that it does not harm the efficiency of your heating and cooling system.
Write for (or instantly download -- www.dulley.com) Update Bulletin No. 404 -- buyer's guide of the best air cleaners, filtration methods, arrestance ratings, prices and an allergen/design selector chart. Please include $3 and a business-size SASE.
James Dulley, The Buffalo News, 6906 Royalgreen Drive, Cincinnati, OH 45244.