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Allergy: Air Filters and Dehumidification
July 3, 2009 |
Air Filters and Dehumidification
It is impossible to eliminate all the airborne allergens that trigger symptoms, but you can reduce the amount of dust floating around your rooms. Forget the old-fashioned fiberglass filters that only capture large particles. That is like trying to catch mosquitoes with a fishnet. We are not big fans of ozone-type air “purifiers” either. The fine folks at Consumer Reports warn that many small room-size ionizing air cleaners (or “electrostatic precipitators”) can generate ozone.25 As far as we’re concerned, ozone is the last thing someone with allergies or asthma needs, since it can be irritating and decrease lung function.
Our first choice in air-cleaning technology is the HEPA
**** Aprilaire Whole-House Air Cleaner
This high-efficiency particulate air (HEPA)-type filter is highly efficient, uses no electricity, lasts 1 to 2 years, and captures most pollen, mold spores, and large dust particles. The box that holds the filter needs to be installed next to your furnace by a heating, ventilating, and air-conditioning (HVAC) professional.
An alternative to the HEPA-type air filter is the Aprilaire Model 5000 Electronic Air Cleaner. Consumer Reports consistently gives this system its highest score.26
Downside: The Aprilaire HEPA-type filter needs to be changed every year or two. Initial installation requires a professional. The electronic alternative is pricey.
Cost: Initial installation of the HEPA filter box is done by your HVAC expert. Should cost less than $200. A packet of two filters is $50 to $60. The Aprilaire Model 5000 Electronic Air Cleaner is roughly $600. Installation can run an additional $200.
(high-efficiency particulate air) filter. These devices are made of densely packed fibers that look like thick paper. The filters are pleated or folded and look like a mini-accordion. That way they maximize the air’s contact with the filter. Industrial-strength HEPA filters are used in computer clean rooms, pharmaceutical manufacturing plants, and hospitals, where it is essential to trap very small dust particles.
To install a whole-house HEPA filter you will need professional help. Ask a heating and air-conditioning (HVAC) expert whether they can retrofit such a system for your home. We think the Aprilaire Media Air Cleaner (formerly Space-Gard) is the place to start (800-334-6011 or on the Web at www. aprilaire.com). This HEPA-type filter achieves 99 percent efficiency for particles bigger than five microns and 95 percent efficiency for the smallest one-micron-sized particles. (Pollen and mold spores usually range from 10 to 100 microns.) The longer you use the filter, the more efficient it becomes, at least to a point. It should be changed every one to two years.
If you cannot afford either a HEPA filter or an electronic air cleaner, consider the less efficient, do-it-yourself 4-inch American Air Filter for around $40 or the 1-inch 3M Filtrete for about $25. These should fit into your existing air return system in place of the old-fashioned filter you may be using.
We find it astonishing that there hasn’t been more clinical research on home air filtration. Pharmaceutical companies have spent hundreds of millions, if not billions, of dollars testing drugs to relieve symptoms. Only a pittance has been devoted to air quality in the home and its relationship to symptom relief.
One review of the available research concluded that “Among patients with allergies and asthma, use of air filters is associated with fewer symptoms. A small study showed that a HEPA air cleaner could reduce the amount of cat allergen levels in the house, but it did not demonstrate improvement in nasal symptom scores.28 Another tiny study showed that a HEPA filter could reduce dog allergens in the air. 29
A pilot study in two daycare centers demonstrated that when a HEPA filter was combined with a dehumidification system, airborne fungal spores were substantially diminished .30 Most people do not realize how serious dampness and humidity are for the home environment. Wherever there is moisture, mold has a marvelous opportunity to multiply. Mold spores can be highly allergenic.
The solution is to get rid of the source of the moisture and keep dampness under control by dehumidifying. The drier your home castle, the less likely it is that there will be mold, mildew, and dust mites. These latter nasty little critters live in mattresses, bedding, carpets, and furniture. Mite poop is also highly allergenic and is responsible for many people’s discomfort. Dry air makes it harder for mites to flourish.
By the way, we used to encourage folks with allergies or asthma to encase their mattresses and pillows with allergen-impermeable bed covers. The goal was to separate the allergy sufferer from the mite poop. Sadly, well-conducted clinical trials have established conclusively that this effort is ineffective.