Indoor air pollution is a monster with dozens of heads, including mold, volatile organic compounds (VOCs), bacteria, viruses, insect droppings, pets, dander, dust, tobacco smoke, dust mites, skin flakes and combustion byproducts. You’d like to slay the Hydra with a single stroke, but it’s not so simple.
The first and least costly step toward reducing indoor air pollution is to attack its sources. Then there are bigger steps. One involves using existing HVAC equipment (heating, ventilation, and air conditioning) to filter air. The other is to install one or more room-dedicated air cleaner. According to the U.S. Environmental Protection Agency (EPA) and the Canadian Home Mortgage Corporation (CHMC) neither approach is entirely satisfactory.
They are at least a half dozen air-cleaning technologies, including mechanical air filters, activated carbon, electro-static precipitators (ESP), ionizers, gas-phase filters and cleaners that use UV light. Each technology has its strengths and limitations. ESP collectors that charge particles as they pass and collect them on oppositely charged collector plates are very tough to clean. Ionizers may smudge nearby surfaces. UV-based methods may be effective in commercial applications but not in homes. A bigger question for all of these technologies is whether enough pollutants ever reach the filter or cleaner.
Adapting Your Furnace
There are three approaches to getting extra duty from your forced-air system in ascending order of cost: upgrade to a higher efficiency filter; install a bigger filter cabinet so you can use a bigger and better filter; or install an ESP filter. The first approach is a bad idea. Slow the airflow too much and the heat exchanger may overheat and crack, releasing carbon monoxide and other pollutants into your home. Installing a bigger filter cabinet, assuming there is room for it, is doable. The bigger (deeply pleated) filters do not have to be changed as frequently and do not restrict airflow very much. Alternately, installing an ESP is expensive, but in the long-term you’ll save on filter replacement costs
Regardless of which approach you choose, CHMC’s Evaluation of Residential Furnace Filters points out that the furnace runs only part time. In addition, pollutants need to be airborne in order to be captured. Research has shown that most aren’t much of the time. They’ve settled into the carpet, bedding, upholstery or on the floor. In fact, CHMC researchers say that particles tend to follow occupants (and pets) around like the dust cloud that hangs over Pigpen’s head in the Peanuts comic strip. Even if some particles are light enough to stay suspended in the air where they can be nabbed by a filter, many of them will never make it to the return grill.
Room by Room
For a few hundred dollars you can purchase a room air cleaner that combines a fan and one or more filters. Some are available with highly effective HEPA filters combined with a pre-filter and carbon filter. Others include high-efficiency filters that are nearly as good as HEPA filters but with lower filter replacement costs
Room air cleaner effectiveness is measured by the unit’s CADR ratings or its clean air delivery rate for various pollutants. Ratings indicate the volume of filtered air delivered by an air cleaner for a specific pollutant. An air purifier with a CADR rating of 300 for dust will deliver 300 cubic feet of dust-filtered air per minute. It will remove other particles, too, but at different rates. Access listings of certified air purifiers and CADR ratings.
The air purifier should be sized according to the square footage of the room and placed where the family congregates, such as in kitchens and family rooms. You can also purchase an air purifier with casters (or add them yourself) and move it to where the action is.
GETTING TO THE SOURCE
The most effective way to reduce indoor air pollutants is to not let them inside or at least to limit their spread. Here are some tips:
• Make your home a no-smoking zone. Limit pet access to a few rooms in the house.
• Close windows when pollen counts are high. Open them when counts are low.
• Remove shoes upon entering the home. Many pollutants and pesticides are simply tracked in Adidas.
• Minimize use of candles and fireplaces, and do not use unvented gas- or kerosene-fueled appliances indoors.
• Control mold by keeping your home’s humidity levels at 50 or less. You can buy a hygrometer to monitor humidity levels.
• Don’t ignore basements and crawlspaces. This air finds its way into the rooms upstairs—with VOCs and mold spores.
• Clean regularly. A vacuum with a high-performance filter is a good investment. Launder sheets and bedding often.
• Dr. Doron Schneider, author of the paper Indoor Air Matters, suggests creating at least one “sanctuary” room in the house. “The master bedroom is a good candidate,” he says. “Pets should be kept out and the room should be as clutter-free as possible, and have bare hardwood floors…”
JOE PROVEY is the author of multiple do-it-yourself books.