Air duct cleaning is an important part of home maintenance. A dirty air duct can lower the quality of the air in your house by promoting the circulation of allergens and bacteria in the air. There is no scientific evidence that actually proves that cleaning the air ducts will improve your health, but it is a good practice. The indoor air is just as important as the outdoor air. One way to keep the air inside your home free from unnecessary pollutants is to keep the air ducts of your heating and cooling systems clean.
When do you need air duct cleaning? There are several signs that indicate the need for a thorough air duct cleaning. Here are some of the major points that indicate the need for an air duct cleaning.

1 The growth of mold inside the ducts or on the surface of the cooling or heating system. (mold growth can only accurately be determined by professionals) 2. The infestation of insects or any small unwanted pests in the ducts. 3. If they are clogged with a great deal of dust or other debris.

It is important to have a professional take a look at your systems occasionally to make sure everything is clean and working well. Certainly if the above problems are prevalent, it is definitely time to go ahead and schedule a cleaning. Make sure the professionals you hire to clean them are licensed. If they claim that there is mold, have them show it to you and figure out a way to prevent the mold from growing again

NADCA experts argue the need for cleaning depends on a variety of factors, including pets, smoking, recent renovations, local weather conditions and overall home cleanliness. Sheppard recommends cleaning them every three to five years. He says a good contractor will offer to do an inspection beforehand for a nominal charge, if any, to see if a cleaning is necessary.

A thorough cleaning can yield long-term energy savings. Bob Baker and Ross Montgomery, who study air quality and energy efficiency for the American Society of Heating, Refrigerating and Air-Conditioning Engineers, say their research shows dirty coils and blowers in commercial buildings can cut efficiency by as much as 40 percent.

NADCA expects to complete its first residential energy efficiency study within the year. Sheppard calls duct cleaning an essential part of home maintenance, akin to mopping and vacuuming. “Because it’s out of sight, people don’t think about cleaning the system that delivers the air they breathe,” he says.

EPA and NADCA agree that if you do hire someone to clean your air ducts, make sure they know what they’re doing – a poor job is worse than no cleaning at all, as it can kick up particles or even break portions of the HVAC system. EPA recommends all duct cleaners follow NADCA standards.

Tom Bergendahl of Wakefield, Mass., wishes he’d hired a reputable service to clean his air ducts instead of a local company that has since gone out of business. “Duct cleaning is a fragile operation, and if you don’t do it right, you can damage the system,” he says. “They completely wrecked the motor.”

The company eventually paid to repair the damage, but Bergendahl still doesn’t feel the work improved air quality or energy efficiency. “Why did I even bother?” he asks.

Despite Bergendahl’s experience, Sheppard says NADCA’s certification standards, developed in 1992, have improved the situation. “A lot of [service companies] weren’t going about it the correct way,” he says.

Other organizations have also established guidelines. The EPA’s brochure available online provides a post-cleaning checklist, and in 2007, the Air Conditioning Contractors of America published criteria for HVAC service providers.

Experts say research on the health benefits of residential duct cleaning is still in its infancy. Glenn Fellman, the Indoor Air Quality Association’s executive director, says that despite the lack of scientific data, he’s seen and heard much common-sense evidence of improved air quality.

“This is the heart and circulatory system of your house,” Fellman says. “If any of it is gunked up with dust or mold, the core system isn’t going to function correctly.”

Ultimately, the decision to clean air ducts comes down to a homeowner’s own judgment. “Get a screwdriver, open up the register and look in there yourself,” Schulte says. “Most can make up their mind at that point.”