While the quality of our environmental air has been a concern for decades, emphasis has now fallen on the quality of indoor air, the air in our homes - air that often contains substances that can irritate our allergies or make us sick.

Research shows that indoor air is often far more polluted than outdoor air, and that many of the particulates commonly found in indoor air are known irritants. About 99% of these irritants cannot be seen with the naked eye.

"One very effective and easy way to greatly improve air quality and comfort in your home is with a whole-house electronic air cleaner," comments David L. Weiner, executive director of the Plumbing-Heating-Cooling Information Bureau. "Far and away, these units remove the highest percentage of particulates in the air that can cause us discomfort and illness."

"Anyone with a sensitivity to smoke, pollen, animal dander, dust mite debris, or who has allergies or a susceptibility to viruses, can breathe easier with a whole-house electronic air cleaner," commented Mary Gould, market manager for Honeywell Inc.

Defining indoor air pollution.

The air in our homes is a combination of millions of small particles and gases. Today, homes are built with tighter construction to help keep energy costs lower. This has the effect, however, of permitting fewer air changes - and of keeping higher concentrations of airborne particulates inside the home.

Untreated, higher concentrations of these particulates can take their toll. Paint, wallpaper, and interior decorating fabrics can become dingier as particulates settle. These particulates also may cause eye and throat irritation, sneezing, headaches and coughs.

What are some indoor air pollutants?

Some particulates found in indoor air are as fine as .01 microns in diameter, or 10,000 times smaller than the diameter of a human hair. Commonly found substances include:

There are three ways to treat an indoor air problem:

Source reduction, dilution, and filtering.  

The best solution to an indoor air problem involves some part of each of these.

Source reduction is attacking particulates at their source. This might involve some drastic measures, such as cutting out smoking and getting rid of pets. These solutions might not always be possible or practical.

Another solution is to dilute the concentration of particulates in the air with cleaner outdoor air. Dilution is desirable because it helps decrease gases given off by carpeting, building materials, and other products.

While some air is continually leaving your home, it may not happen at a very high rate in tightly-constructed homes. To speed up dilution, you can open windows and doors to let in more outdoor air. This, too, is not always practical or possible.

The third solution, filtering the indoor air supply, can take several routes. Almost every home has a basic furnace filter, which prevents the biggest particulates, such as lint, hair and large dust, from getting into the furnace. These filters operate at a cleaning efficiency of about 5% at best (meaning that they remove about 5% of all the particulates in your air).

You can insert an electrostatic filter in your furnace. Made of materials such as polystyrene or polypropylene fibers, these filters have a built-in electrostatic field designed to charge and attract particulates. However, they don't remove as much as an electronic air cleaner. People prefer them because they are less expensive, washable, easier to clean, and are non-electric.

Another type, a media filter, is formed of paper or fiber material on a frame. The pleated fabric is designed to expose much more surface area than a basic filter, and these filters are much thicker. These work in part by straining particulates larger than the spaces between the filter fibers from the air stream.

One of the drawbacks of these filters is that they can cause a pressure drop in your heating-cooling system as the filter gets dirtier, meaning that your furnace must work harder to pull air through the filter and the rest of the system. But an advantage is that they are once again, less expensive than an electronic air cleaner and go a long time between changes. This is great if the unit is in tough to get to area like an attic or crawl space. Easy to install, no electrical wiring, no parts to break.

Another way of treating indoor air problems is with an electronic air cleaner. Electronic air cleaners effectively remove nearly all airborne particulates. Placed in the cold air return duct of your furnace, these units remove up to 95% of particulates from the indoor air supply, greatly improving indoor air quality while helping protect the heating system from the ill effects of dust and dirt, and keeping the home cleaner.

Electronic air cleaners remove airborne particulates that filters can't, including nearly all of such small irritating particles as bacteria, pollen, spores, animal dander, viruses and cooking and cigarette smoke. And they have the lowest pressure drop rating of any filtering system (.08 wc) - while helping keep your heating-cooling investment running as cleanly and efficiently as possible.

Electronic air cleaners work differently than basic, electrostatic, or media filters. They give particulates in the air stream a strong electrical charge, then collect and trap them on oppositely-charged plates.

Incoming air passes through a prefilter to remove larger particles. Then, particulates are given a strong positive or negative charge as they pass through a series of ionizing wires. In he collection section, the charged particles are attracted to an oppositely-charged plate, where they stay until the unit is cleaned. Some units manufacturers offer may include a charcoal filter to help reduce household odors.

Cleaning is simple. Just remove the collection cells three to four times a year, wash with household cleaner to remove contaminants, soak in a laundry tub or place in the dishwasher.

Making a wise air cleaner buy.

How can you make a decision on the filtering system that's right for you? "Pay close attention to the efficiency claims," advises Dave Cenedella, product manager for White-Rodgers' Electro-Air air cleaners. "But you need to know the type and size of particles being filtered out of the air supply. Because some irritants, such as cigarette smoke particles, are so small, you will get the most benefit from an electronic air cleaner that has high effectiveness against particulates as small as .01-.03 microns."

Another consideration is cost, and you should calculate this to extend over a ten-year period, advises Honeywell's Gould. Weigh initial costs versus replacement or maintenance, and consider that a whole-house electronic air cleaner can help protect your heating system investment. Honeywell offers a Clean Coil Guarantee, with the promise that if coil cleaning is required within ten years of installation of one of its electronic air cleaners, the company will pay half the cost of the cleaning.

Leave installation to a professional.

You can plan on installing an electronic air cleaner when you replace your furnace or central air conditioning, or when you're building a new home and selecting a heating-cooling system. If funds don't allow you to install an electronic air cleaner right away, an alternative is to put in an electronic air cleaner compartment with a media filter. Later, you can upgrade your system by having a licensed, professional heating-cooling contractor install an electronic air cleaner in the compartment.

Installation of a whole-house electronic air cleaner is the province of a professional heating-cooling contractor. "A professional is best qualified to help you determine the capabilities of the unit you need for your home, and how you maintain it. He should definitely be your choice for doing the installation and electrical connections.