Better Airflow

By Amy Winter

May 2, 2008 5 min read


Replace filters to reduce need to clean dirty ducts

By Amy Winter

Copley News Service

Dirt and allergens enter the house on a daily basis, building up in your home's ducts and clogging your heating and cooling system.

There is no evidence that routine duct cleaning will prevent health problems, says Bob Formisano, a home-repair columnist for, but consistent maintenance of will ensure everything is working properly, preventing fires in dryers and debris buildup in air conditioning/heating systems.

Regular filter maintenance can reduce the need for air duct cleaning. Tim Carter, a custom home builder who runs the Web site, advises homeowners to keep filters clean. Depending on the quality of the filter, some will last longer than others. Paper filters need to be changed every 30 to 45 days, according to Carter. Higher-quality filters can be washed off and reused. John Schulte, executive director of the National Air Duct Cleaners Association, recommends not waiting longer than three months to clean or replace filters. And make sure the filters fit properly.

"If you keep filters clean, ducts should have less dust," says Carter.

Dirt enters the ducts due to a poor job by the filters, according to Formisano. The Environmental Protection Agency says a majority of the dirt sticks to the duct surface - it usually doesn't dislodge on its own. But some particles can become airborne due to traveling vibrations in the air system, according to Schulte.

Buildup of dirt and dust may affect airflow. The loss of air pressure throughout the unit can mean running the system longer in order to heat or cool the house. Schulte recommends looking at the coils for dirt blockage. Dirt will stick easily to the wet metal coils due to increased condensation, which is formed as humidity is taken out of the airflow.

You might opt for more frequent duct cleanings if you have smokers in the house, excessive pet hair and dander, water damage or highly allergic inhabitants, according to the NADCA. But duct cleanings are more essential when there is evidence of a problem involving mold, moisture, large amounts of debris or dust, or rodents and insects.

Schulte suggests inspecting the unit at least once a year. Make sure to look at the coils and blowers. Examine the amount of dirt in the ducts every two years. Take a picture with a digital camera or use a mirror or flashlight to see inside the vent.

If you see large amounts of dirt or debris and feel your air ducts should be cleaned, make sure you choose a company that is part of the NADCA standard, which includes assessment, cleaning and restoration. Schulte says to stay clear of ads for cheap specials. You need to go with professionals for air duct cleaning - avoid doing it yourself. Carter says the the process is "not an easy task."

"If they don't do the cleaning right, they are dislodging dust," he says.

The entire system must be cleaned under negative pressure, which is produced with a high-powered vacuum, according to the NADCA standard. Once the vacuum pulls air through the system, agitation tools are used to scrap dirt off the duct surfaces. The dirt and debris moves from the duct to the vacuum, eliminating it from the system and the home. The vacuum collection machine is either attached to trucks or portable units. Make sure all the dislodged dirt is removed from the system; you don't want it blowing into your home.

It is important to regularly wipe the lint trap on the dryer, but proper dryer maintenance also includes cleaning the dryer duct. Todd Peach, vice president of operations at In-O-Vate Technologies, says it can be a do-it-yourself project. Buy a kit that contains tool brushes. The LintEater system by Gardus includes a flexible rod that can snake up to 12 feet of venting, a 4-inch rotating auger brush, a vacuum cleaner adapter to suck up lint, a dryer-blower adapter and a blockage-removal tool.

Failure to clean blocked dryer ducts is the top reason for dryer fires - approximately 42 dryer fires occur each day, according to the U.S. Fire Administration's 2007 study. Inspect the ducts every six to 12 months: Make sure the vent isn't clogged by lint buildup, debris or bird nests, according to Clean if you notice blockage.

"Feel for proper exit velocity of the air leaving the vent," according to "And look at or feel the interior walls of the duct. Clean, unobstructed, frictionless ducts encourage air flow efficiency, quickens drying times, adds longevity to clothing's life and reduces utility bills."

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