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Newer Tighter Homes, Older Stagnant Air

Indoor air quality - IAQ - how significant is it and should you be concerned? Perhaps more importantly, what can you do about it?

Unfortunately, the air in our homes is some of the dirtiest we breathe, even dirtier than that found along many of our highways. There are many reasons - pets, fabrics that retain dust and debris, plants (a source of pollen) and casual house cleaning, among others. So you probably should be concerned, especially if you or someone in your family has asthma, allergies or other respiratory sensitivities.

Air pollutants can be particulate matter (dust), odors, gases, smoke, viruses or house-dust mites, among others. Chemical or biological contaminants can also be a concern. Some sources are airborne; some are not. Control is difficult, and in some cases, it is impossible or impractical.

Air filtration is one way to improve indoor air quality. Various types of freestanding air filters are enjoying great popularity as many people have decided that they are the answer to improving the air quality in their homes (and cars). But are they the answer? And are they worth the investment?

Let's review the basics of air filtration.

First, there are basically two types: central or local filtration. A central system that filters virtually all of the air in your home is generally more effective than a local or freestanding unit. The ability to affect most or all of the air in your home is much higher. Central filtration systems are more effective but also more expensive to install. Such systems are also limited to homes with central heat and/or air-conditioning, since a duct system to circulate the air is needed. Most warm air heating systems do include some central filtration. The filters need to be replaced frequently, and the ductwork should be cleaned regularly for optimum performance. A freestanding unit can affect only a small, local volume of air, which will then mix with the other air in your home.

Second, there are two primary methods of filtration. You can clean the air either mechanically, by filters that trap particles, or electronically, by systems that attract particles on electrically charged plates.

Mechanical filtration results vary according to the quality and condition of the filter. The most effective are HEPA (high efficiency particulate arrestant) filters. They are also the most expensive. All filters need to be replaced on a regular basis to maintain optimum air cleaning effectiveness.

The effectiveness of electronic filtration depends on the quality of the unit, as well as the volume of air it can process, and proper maintenance. Some electronic units produce ozone, which is considered by many experts to be an air pollutant that can cause respiratory problems.

Even the best air cleaning devices cannot ensure good air quality. They will not affect pollutants such as gases or viruses. They will have only limited effect on airborne particulate matter, depending on the quality of the filter and how well it is maintained. They will not affect dust mites or similar material that is not airborne.

So, should you buy or install an air filtration system? If someone in your family suffers from asthma or allergies, the answer may be yes. But realize that you will not be producing pure, contaminant-free air, only improving it. If no one is suffering from asthma or allergies or if you just want to take a more practical approach to improving the air quality in your home, the list to the left includes some things you can do that don't involve buying and maintaining new, often expensive, appliances or equipment.

If you can't say "I am doing that" or "I will do that" to a majority of the items in the list on the left, buying one of the popular "air cleaners" is not going to do much for you. At best, you will be dealing with the symptom more than the cause and, even then, with only limited effectiveness.