QUESTION: Each spring and early summer my daughter suffers from allergies. She seems to be allergic to pollens in the air. We live near a large area of meadows and trees. When she stays indoors, it seems to help, but she still has problems.
Are there ways I can keep the dust and pollens out of my house or devices we can use to clean the air?
ANSWER: Pollens are very small particles that can easily pass through the cracks and joints in houses and through the filters on typical residential furnace and air conditioning systems.
The first step to take is to keep as many pollen particles out of your home as you can. Make sure your home is weatherstripped and caulked to the degree possible. Once you've blocked all of the unintentional openings, the fresh air entering your house should be filtered on its way in . . . or the pollen removed once it has entered the home.
The ideal situation is a well-sealed, draft-free house and a mechanical ventilation system that incorporates air filtering to remove dust and pollens from the incoming air. Mechanical ventilation systems can also provide heat recovery, as in the case of air-to-air exchangers. Obviously, in your daughter's case, open windows are not the complete answer to fresh air needs.
Whether your fresh air is provided by a mechanical ventilation system, or is simply outdoor air that has leaked or infiltrated into your home, you will need adequate filtering equipment. This can be installed in central heating/air conditioning and ventilation systems for whole-house air cleaning, or if you do not have a central system, there are through-the-wall and portable, stand-alone, units available.
Types of Equipment:
Two types of air cleaning equipment commonly used for removing small particles such as pollen are mechanical filters and electronic air cleaners.
Mechanical filters--Mechanical filters generally consist of a fibrous or mesh material that simply strains the particles out of the air stream as it passes through the filter.
These can be located in forced-air heating/cooling systems, ventilation systems, or in through-the-wall ventilation units (with and without heat recovery).
You didn't mention if you had a forced-air heating/cooling system. If you do, you can replace the typical throw-away furnace/ac filter with one that is effective for small particles. The filters found in most homes are designed to filter large objects such as pet hair, leaves, etc. They are virtually worthless for small particles such as pollen.
A low-tech option, that may help somewhat, is to use a 2-inch or 4-inch thick, medium efficiency, pleated filter. These cost from $4 to $20 each. While these will remove only some of the pollen particles, they will definitely work better than the typical furnace/ac filter.
To remove most of the pollen you will need a high-efficiency (HEPA) filter. These are generally at least 12 inches thick and cost between $50 and $200 each. While expensive, they will filter more than 99% of the pollen from the air!
Generally, mechanical filters are not washable. As they become dirty they must be replaced. Filters may need to be changed as often as every month, depending upon how many particles are in the air stream. Obviously, replacement costs are a consideration with these mechanical filters.
Most residential systems have a 1-inch slot in the ductwork for the filter. Obviously, you will need to have your system modified to handle the 2-, 4-, or 12-inch filters. Also, the basic performance of your heating/cooling system can be adversely affected by these filters. They can restrict the air flow through your furnace or air conditioning unit.
Make sure the filter you use is compatible with your system. Obviously, these filters will only work when the system fan is operating. You may want to run the fan continuously at low speed during periods when maximum air cleaning is desired.
Electronic Air Cleaners--Electronic air cleaners are another option. They work by charging the particles as they pass through an electric field. These charged particles are then collected on metal plates that have an opposite electrical charge.
These are very effective for small particles, similar in performance to the HEPA filters. Prices range from $200 to $700. Keep in mind that a one-time cost for an electronic air cleaner may make more sense than repeated purchases of a $200 HEPA filter.
These are available for central heating/cooling systems AND in portable, stand-alone models, very important if your home has a baseboard, radiant or other zonal-type system. If you do have a central system, the filters are usually installed in the ductwork immediately down-stream from the regular filter.
Since cleaning is important, make sure the cell(s) are easily removed for cleaning.
At first glance these air cleaning options look expensive--but consider the benefits compared to your daughter's discomfort and ill-health, or the very real costs of doctor bills and prescriptions.
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