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“High-Efficiency” Furnace Filters

Standard furnace filters don’t remove small respirable dust particles. Furnace filters are instead designed to keep your furnace and air-conditioning coil clean. Since your furnace’s heat exchanger and air-conditioning coil have narrow, hard-to-reach passageways, they are quite difficult to clean. When they get dirty, the efficiency of your heating and air conditioning system will suffer, and your equipment’s lifespan will be reduced.

In recent years, consumers have purchased millions of air-cleaning or air-purifying furnace filters to reduce dust levels in their homes and to hopefully improve their respiratory health. But many researchers have asked, “Are these filters effective?” The answer depends on your definition of effective. If effective means that the filters catch small dust particles and perform to their advertised specifications, the answer is “yes.” However, if the definition of effective is substantially reducing the amount of dust that you breathe, then the answer is “probably not.”

Researchers for the Canada Mortgage and Housing Corporation (CHMC) have discovered that your activity level around the house is the leading determinant of how much dust you breathe, since we all tend to stir up dust as we perform our daily activities. The CHMC research shows that while the furnace filters are catching plenty of dust, they can’t really keep up with the production of dust by active families.

If you must reduce dust for acceptable respiratory health, a good furnace filter is an excellent start. But it should be just part of a multifaceted strategy that includes as many of the following guidelines as possible.

Electronic air cleaners are highly effective at removing fine dust but they load up with dust very rapidly. Effectiveness at collecting dust and improvement in air quality are two different things.

Remove your shoes when you come indoors.
Don’t smoke in your home.
Don’t allow pets indoors.
Install hard surface floors–such as vinyl, tile, or wood– rather than carpet in high-traffic areas of the home.
Improve your home’s airtightness to exclude outdoor dust as well as save energy by installing weatherstripping and by sealing air leaks in walls, floors, and ceilings.
Invest in a HEPA (high-efficiency particulate air) vacuum cleaner, rather than a standard vacuum cleaner, so that you don’t redistribute dust when vacuuming.

See The Homeowners Handbook to Energy Efficiency or Residential Energy: Cost Savings and Comfort for Existing Buildings Chapter 6 for more information. For professional information about heating systems and energy efficiency see Saturn Mechanical Systems Field Guide.