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TECHNOLOGY AND YOU

Clean the air

small air cleaners work more efficiently

Q: Dear Jim: I run my furnace blower continuously so that the central air cleaner is more effective. Does it make sense to use room air cleaners in addition to the central one or does that just waste electricity? - Ann R.

A: Dear Ann: Many people are now running their furnace blowers continuously for better indoor air quality, especially in efficient, airtight houses. Most blower motors, unless you have a new variable-speed air handler, use a considerable amount of electricity when you run them continuously. The newer variable-speed blowers use about two-thirds less electricity.

In most cases, depending on the type of particles (allergens) that you are trying to remove from the indoor air, running several small room air cleaners can be more effective. You will probably want to use different types of room air cleaners for different rooms and air quality problems. In addition, they will probably use a lot less electricity overall than running the blower continuously.

In addition to indoor air quality, a primary purpose of any central air cleaner/filter is to keep the furnace/heat pump heat exchanger surfaces and coils clean. If they get dirty, their ability to transfer heat is reduced. This results in lower efficiency and higher electric bills. They also require care because, as they become dirty, they increase the resistance to airflow through the furnace or heat pump.

Good quality central air cleaners are most effective for removing tiny particles, like smoke that tend to stay airborne. Most common allergens, like pollen, dust mite feces, mold spores, etc., are larger particles.

After you walk on the carpet or plop down on a sofa creating a cloud of them, these larger particles settle back down before they enter the return registers. For removal of these larger particles, individual room air cleaners can be very effective.

When you go to your home center store, you will see dozens of room air cleaners with glowing claims of effectiveness on their packaging. Actually, the two most effective room air cleaners are "true" HEPA (high efficiency particulate air) and electrostatic (electronic) designs.

I have just installed an efficient electronic central air cleaner in my own heat pump. I also use HEPA room air cleaners in my bedroom and home office where it gets dusty and an electronic model in my family room by the woodburning fireplace to take care of smoke.

A HEPA air cleaner works by forcing the room air through a very dense filter media. HEPA filters were

James Dulley is a mechanical engineer who writes on a wide variety of energy and utility topics. His column appears in a large number of daily newspapers.

Copyright 1999 James Dulley

18 ILLINOIS COUNTRY LIVING • FEBRUARY 2001

originally designed for use in hospital operating rooms. To be a true HEPA, it must remove 99.97 percent of all particles down to .3 microns in size. This includes almost all allergen particle sizes. When selecting one, watch for terms on the packaging like "HEPA-like" that may not be as effective as a true HEPA.

With the very dense filter media, HEPA air cleaners require fairly powerful blower motors (100 to 150 watts of electricity) to force the air through the filter. This consumes more electricity than electronic models. If you also want to remove odors, select one of the HEPA air cleaners with a large carbon element. The more powerful motor allows a heavier carbon filter to be used. The replaceable HEPA filter elements usually last from one to three years.

Electronic air cleaner models have several sets of elements inside the cabinet. The first set of elements electrically charges the particles in the air. The second set of elements (collector plates), in the washable assembly, has the opposite charge so the particles stick to them. Often there is also a thin prefilter to catch very large particles. Every month or so, slip out the assembly and wash it in your dishwasher.

Since there is no dense filter, a less powerful blower motor is needed to draw the room air between the collector plates. This uses less electricity (the charging portion uses very little electricity) than a HEPA unit and some may operate quieter. Electronic air cleaners are particularly effective for removing tiny airborne particles like fireplace or cigarette smoke.

It is wise to select a model with several fan speeds (three or more), especially if you plan to use it in a bedroom at night. Ones with large carbon after-filters will remove some volatile chemicals in addition to odors.

When selecting a room air cleaner, CADR's (clean air delivery rating) are a good reference to compare the effectiveness of the various models. Each room air cleaner is tested under controlled conditions to determine how well it removes smoke, pollen and dust. This rating (usually shown on the packaging) will help you to determine which specific model is best for various allergens and various sized rooms.

Write for (instantly download -www.dulley.com) Utility Bills Update No. 885 - buyer's guide of 15 manufacturers of effective room air cleaners listing types, speeds, recommended room sizes, features, prices, CADR's and an allergen size chart. Please include $3.00 and a business-size SASE. James Dulley, Illinois Country Living, P.O. Box 54987, Cincinnati, OH 45254.

FEBRUARY 2001 • ILLINOIS COUNTRY LIVING 19