Is Air Duct Cleaning Worth It?

Experts agree there is value to air duct cleaning, although there’s no scientific evidence it improves air quality.

Linda Wetzel of Shaker Heights, Ohio, says she was skeptical about air duct cleaning until a friend told her it had improved her allergies. “I figured common sense said, if there’s dust on the table, there has to be dust in the vents,” Wetzel says.

After hiring an air duct cleaner she found on Angie’s List, Wetzel was very pleased with the results and benefits she experienced. She says she noticed an immediate improvement in air quality — everyone in the house suffered fewer allergies afterward — and the entire HVAC system worked more efficiently.

“We used our air conditioner less in the summer because it had so much more airflow,” she says. “And we used the heater less during an incredibly cold winter.”

Despite such anecdotal experiences, there’s no scientific evidence that regular residential air duct cleaning improves air quality, according to a 1997 brochure published by the Environmental Protection Agency. Laureen Burton, senior scientist in the EPA Indoor Environments Division, says that while the document is nearly two decades old, the science hasn’t changed and the agency stands by its recommendations.

“Checking and changing filters, keeping systems maintained, having regular inspections, and ensuring moisture doesn’t get in are more important,” Burton says.

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before and after photo of dirty air duct and clean air duct

The top photo shows the dirty air duct before cleaning, and the bottom photo shows the clean air duct after. (Photo by Eldon Lindsay)

However, both EPA and the National Air Duct Cleaners Association — which represents more than 1,000 cleaning companies nationwide — agree there’s some benefit in cleaning debris from ducts, furnaces, central air conditioners and ventilation.

NADCA consulted on the EPA pamphlet and agrees with all but one of its findings, according to NADCA president Michael Vinick. He says NADCA recommends homeowners clean their ducts once every three to five years. “If you have allergies or asthma, you should consider having it done almost annually,” he says.

The EPA does not recommend that air ducts be cleaned routinely, but only as needed — such as when mold, pests or excessive debris clutter the system. In an online poll, 13 percent of Angie’s List members said they have their ducts cleaned routinely, but 60 percent do so only if serious problems develop.

When do I need to get my air ducts cleaned?

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. Vinick says a good contractor will offer to do an inspection beforehand for a nominal charge, if any, to see if a cleaning is necessary.

NADCA’s standards dictate that a cleaning doesn’t just sweep the ducts, but addresses every component air passes over, including coils and the central system. The task involves at least a couple of workers, several hours and costly equipment, which is why air duct cleaning costs $400 or more, according to EPA and NADCA.

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.

Vinick calls air duct cleaning an essential part of home maintenance, akin to mopping and vacuuming. “It’s like changing the oil in your car,” he says. “If you don’t change the oil, you’re going to have a problem. When your components are loaded up with debris, the system has to work harder. When you rem

Should chemical biocides be applied to the inside of air ducts?

Summary

Knowledge about air duct cleaning is in its early stages, so a blanket recommendation cannot be offered as to whether you should have your air ducts in your home cleaned. The U.S. Environmental Protection Agency (EPA) urges you to read this document in it entirety as it provides important information on the subject.

Duct cleaning has never been shown to actually prevent health problems. Neither do studies conclusively demonstrate that particle (e.g., dust) levels in homes increase because of dirty air ducts. This is because much of the dirt in air ducts adheres to duct surfaces and does not necessarily enter the living space. It is important to keep in mind that dirty air ducts are only one of many possible sources of particles that are present in homes. Pollutants that enter the home both from outdoors and indoor activities such as cooking, cleaning, smoking, or just moving around can cause greater exposure to contaminants than dirty air ducts. Moreover, there is no evidence that a light amount of household dust or other particulate matter in air ducts poses any risk to your health.

You should consider having the air ducts in your home cleaned if:

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There is substantial visible mold growth inside hard surface (e.g., sheet metal) ducts or on other components of your heating and cooling system. There are several important points to understand concerning mold detection in heating and cooling systems:

  • Many sections of your heating and cooling system may not be accessible for a visible inspection, so ask the service provider to show you any mold they say exists.
  • You should be aware that although a substance may look like mold, a positive determination of whether it is mold or not can be made only by an expert and may require laboratory analysis for final confirmation. For about $50, some microbiology laboratories can tell you whether a sample sent to them on a clear strip of sticky household tape is mold or simply a substance that resembles it.
  • If you have insulated air ducts and the insulation gets wet or moldy it cannot be effectively cleaned and should be removed and replaced.
  • If the conditions causing the mold growth in the first place are not corrected, mold growth will recur.
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Ducts are infested with vermin, e.g. (rodents or insects).

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Ducts are clogged with excessive amounts of dust and debris and/or particles are actually released into the home from your supply registers.

If any of the conditions identified above exists, it usually suggests one or more underlying causes. Prior to any cleaning, retrofitting, or replacing of your ducts, the cause or causes must be corrected or else the problem will likely recur.

Some research suggests that cleaning heating and cooling system components (e.g., cooling coils, fans and heat exchangers) may improve the efficiency of your system, resulting in a longer operating life, as well as some energy and maintenance cost savings. However, little evidence exists that cleaning only the ducts will improve the efficiency of the system.

You may consider having your air ducts cleaned simply because it seems logical that air ducts will get dirty over time and should be occasionally cleaned. Provided that the cleaning is done properly, no evidence suggests that such cleaning would be detrimental. EPA does not recommend that the air ducts be cleaned routinely, but only as needed. EPA does, however, recommend that if you have a fuel burning furnace, stove or fireplace, they be inspected for proper functioning and serviced before each heating season to protect against carbon monoxide poisoning.

If you do decide to have your air ducts cleaned, take the same consumer precautions you normally would in assessing the service provider’s competence and reliability.

Air duct cleaning service providers may tell you that they need to apply chemical biocide to the inside of your ducts as a means to kill bacteria (germs) and fungi (mold) and prevent future biological growth. They may also propose the application of a “sealant” to prevent dust and dirt particles from being released into the air or to seal air leaks. You should fully understand the pros and cons of permitting application of chemical biocides or sealants. While the targeted use of chemical biocides and sealants may be appropriate under specific circumstances, research has not demonstrated their effectiveness in duct cleaning or their potential adverse health effects. No chemical biocides are currently registered by EPA for use in internally-insulated air duct systems (see Should chemical biocides be applied to the inside of air ducts?).

Whether or not you decide to have the air ducts in your home cleaned, preventing water and dirt from entering the system is the most effective way to prevent contamination (see How to Prevent Duct Contamination).