Duct Cleaners

Don’t Hire Duct Cleaning Companies

Ignore deceptive ads and claims; you likely don’t need their services.

For many years, we’ve warned that HVAC system duct cleaning usually is a big waste of money.

Yes, your ducts can get dirty. But air-quality experts consistently agree that cleaning them provides no measurable benefit, even for those with allergies or asthma.

Even if your ducts are filthy, cleaning them likely won’t lower dust levels throughout your home. Dust that settles in your ventilation system generally stays put, unlikely to become airborne unless disturbed. Under most circumstances, it is inert and harmless—and stirring it up with cleaning equipment might actually create bigger problems.

What Duct Cleaners Do

To clean ductwork, companies place the system under negative pressure—essentially connecting a very large, powerful vacuum cleaner to one or more openings and sucking out loose dust and other debris. Because a vacuum isn’t powerful enough to loosen and remove all particles, duct cleaners must agitate the dust using a rotary brush, compressed air nozzles, and a tool called a “skipper ball.” They also should clean the heating and cooling equipment (heat exchangers, cooling coils, condensate drain pans, fan motors, fan blades, and fan housings), but that work isn’t always included in their basic cleaning service (most cleaning companies charge $450 to $1,000).

Note: While HVAC ducts do not require regular cleaning, the exhaust hose for your dryer, which can become clogged with lint, does need regular inspection to avoid a fire hazard. Click here for details on getting this work done or doing it yourself.

Why You Don’t Need It

The duct-cleaning industry promotes a solution in search of a problem. Although these businesses may claim their services are essential for your health, the evidence is lacking. The dust lurking in your vents generally stays there unless disturbed.

Unfortunately, many duct-cleaning companies continue to mislead customers, often promising health benefits. Some ads even use language like, “Studies have shown...” But no data back up these claims. Other companies, plus their trade association, suggest that duct cleaning will lower your power bills by improving your system’s efficiency. That’s also dubious.

Air-quality experts don’t recommend regular duct cleanings. The official advisory of the U.S. Environmental Protection Agency (EPA) concludes:

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... Moreover, there is no evidence that a light amount of household dust or other particulate matter in air ducts poses any risk to health.

Little independent research has been done on the effects of duct-cleaning work. The Canada Mortgage and Housing Corporation (CMHC) conducted a study in the 1990s to investigate whether duct cleaning makes indoor air healthier or reduces energy costs by improving airflow. After testing 33 homes in Montreal before and after professional duct cleaning, the study found no significant improvement in air quality and that duct cleaning alone did not improve airflow or energy efficiency. In some cases, measured particle levels actually increased immediately after a cleaning. In other cases, particle levels decreased immediately after cleaning, but returned to previous levels within weeks.

Like the EPA, the CMHC concluded that duct cleaning is unnecessary:

A thorough duct cleaning done by a professional duct cleaner will remove dust and debris… However, duct cleaning will not usually change the quality of the air you breathe, nor will it significantly affect airflows or heating costs.

The CMHC study called on several different duct-cleaning services. The companies were not made aware they were part of a study, and the researchers did not control for time spent or methods used.

While the duct-cleaning industry argues that CMHC’s study has flaws, no other independent research has challenged its findings. And although the equipment and methods used by these companies have changed since CMHC’s study was conducted, the air ducts in homes and the dust remain the same.

In 2010, M. S. Zuraimi, a researcher with the Canadian National Research Council’s Indoor Environment Research Program, reviewed previous studies of duct-cleaning effectiveness and concluded that “no field studies have correlated poor IAQ [indoor air quality] with duct contamination,” and that “post-cleaning air pollutants concentrations can be higher than pre-cleaning levels. Further, there are health concerns in the use of biocides, sealants and encapsulants” that some companies routinely spray into HVAC systems.

No U.S. public health group or government entity focusing on air-quality issues—the EPA, National Institutes of Health, American Lung Association, Asthma and Allergy Foundation of America, or World Asthma Foundation—recommends regular duct cleaning.

Want to Control Dust? Here’s What Actually Works

Frequently changing air filters is the best way to keep dust, allergens, and other particles out of your home. With a newly installed system, or a system in a home you’ve just moved into, check your filter monthly to determine how quickly it gets dirty at different times of the year. Most filters should be replaced every two or three months.

To further reduce dust and other allergens throughout your home, the Asthma and Allergy Foundation of America recommends:

• Establish regular cleaning routines.
• Keep windows closed during peak pollen times or during times of high outdoor pollution.
• Remove strong scents like candles and avoid harsh cleaners.
• Consider replacing carpet with solid-surface flooring.
• Wash bedding weekly.

Visit AAFA.org for additional recommendations, including specific tasks for bedrooms, bathrooms, living areas, and kitchens.

Duct Cleaning Won’t Save Much Energy, Either

Another sketchy claim made by most duct-cleaning operations and their trade association: Dirty ducts and equipment overburden heating and cooling equipment, wasting energy. It may seem as if a cleaner system will run more smoothly and last longer—after all, that’s why we and HVAC equipment manufacturers and repair services recommend that you regularly change your filters. But the page “Why Clean Air Ducts?” on the National Air Duct Cleaners Association (NADCA) website stretches the truth: “According to the U.S. Department of Energy, 25 to 40 percent of the energy used for heating or cooling a home is wasted. Contaminants in the heating and cooling system cause it to work harder and shorten the life of your system.”

This statement is misleading. Although much of the energy used to power heating and cooling equipment is indeed wasted, the Department of Energy’s estimates of energy waste clearly indicate that the vast majority of it occurs due to inefficient equipment, leaky ductwork, and homes passively allowing conditioned air to escape.

Researchers for the Canadian duct-cleaning study found that when duct cleaners also clean the blower fan blades, there was a small reduction in airborne particles. (This might slightly improve your system’s energy efficiency, too.)

NADCA’s website points to a recent study published by researchers who ran tests in commercial buildings located in cities in four different climate regions, where they measured energy consumption before and after duct cleanings. They found “significant energy savings observed in response to routine HVAC cleaning.” But the study’s authors noted that their analysis “also indicated that larger systems, in terms of ductwork conveyance and cooling capacity, benefited more from cleaning than their smaller counterparts.” Although they didn’t study the effects of duct cleanings in homes, they acknowledge that “In smaller systems, the larger relative energy benefit is realized from coil cleaning.”

If you’re concerned about energy waste, see our section Saving Energy at Home. Key tasks include having your duct system inspected for leaks, since leaky ducts lower efficiency and introduce air-quality problems, and sealing up leaks around doors, windows, and other trouble spots.

One HVAC-related chore that might provide significant benefits is regularly cleaning cooling-system evaporator coils. They cause condensation, dehumidifying the air before it circulates through your home. Condensed moisture can cause dust and other particles to build up on the coils. Also, cleaning the collector pan (and the drain spout in it) beneath the coils ensures that dirt doesn’t build up and get drawn into the system. It also prevents water, which can cause mold problems, from accumulating on and beneath the coils.

But we don’t recommend hiring a duct cleaner to perform these tasks; too many don’t know what they’re doing. We have ratings of duct-cleaning outfits here at Checkbook.org, but consider hiring a top-notch heating and air-conditioning contractor instead—or pay them to do it during their next service visit.

Cleaners Might Damage Your Ducts and Home

Another reason to avoid duct cleaners: Performed improperly, duct cleaning can do more harm than good.

If the vacuum pressure isn’t applied carefully, some of the dust in the ducts will be loosened by the agitation and blown into the living space. (This explains the results of the Canadian study in which particle levels actually rose immediately after a cleaning.)

Running brushes or using compressed air also risks breaking seals in the duct system, which can be especially problematic in the return-air portion. Most forced-air systems are designed as closed loops, and leaks in the return-air circuit allow unfiltered air to be sucked from basements or attics, bringing with it dust and moisture.

Not every home contains sheet-metal ductwork. Flexible coil-style ducts—the kind that look like Slinkies—are more prone to punctures and other damage.

Ductwork fabricated from fiberglass-insulated material—less expensive than metal—has become more common in new homes. These ducts have fiberglass insulation on their interior surfaces. The fiberglass surface is sealed, but if a duct-cleaning company is not careful, the cleaning can damage the insulation, loosening fibers that can become airborne.

And, of course, there are the usual types of problems that can occur when you deal with any contractor—evidenced by the negative customer reviews some companies receive here at Checkbook.org.

Problems That Warrant a Cleaning

In general, consider duct cleaning only in response to specific identifiable problems. The EPA suggests doing it only if there is visible evidence of:

• Substantial mold growth (but see below)
• Infestation of insects or rodents
• Substantial deposits of dust or debris (if registers were not sealed during a renovation project, for example)

But the EPA also notes that hiring a duct cleaner to resolve one of these problems isn’t a permanent solution: “If any of the conditions 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.”

If anyone in your household has specific health concerns, such as allergies or asthma, consult your physician first. It’s important to identify the problem, so your doctor can suggest alternatives to duct cleaning. Start by identifying whether your ducts are part of the problem (they probably aren’t) and whether getting them cleaned will help (it probably won’t).

Think You Might Have Mold?

If you suspect a mold problem—either because of visible growth or a musty smell constantly coming from supply vents—cleaning ducts won’t do much good if it doesn’t eliminate the mold. Mold always begins with a moisture problem, and the ducts themselves are unlikely to be the source. The most likely culprits are the cooling system’s evaporator coils, which your heating and air-conditioning contractor—and most duct-cleaning companies—can inspect and maintain. Leaky return ducts can also introduce moisture. Again, if you suspect mold, have a service company inspect the duct system for leaks. If you think—but aren’t sure—that what you see is mold, you can get it tested for about $50. But experts we consulted generally recommend against it, reasoning that:

• Mold is present in all homes; it becomes problematic only when there is a moisture problem.
• Rather than paying for testing, it’s better to track down and eliminate moisture problems—whether under a sink or part of a heating and cooling system.

Still Hiring a Cleaner? Here’s What to Look for

If you decide to have your ducts cleaned anyway, don’t hire a company that makes sweeping claims about health benefits or that it’s “EPA-certified” for duct cleaning. There’s no such certification.

Here at Checkbook.org, you’ll find customer reviews of duct-cleaning outfits. We also evaluate HVAC services, which are better bets for equipment servicing and cleaning (although some do push unnecessary duct-cleaning work).

Shop for a good price. Consumers’ Checkbook’s undercover shoppers collected price quotes from a handful of local companies for a straightforward duct-cleaning job, including equipment cleaning, and found huge company-to-company price differences among bids based on identical specifications. Quotes for our sample home ranged from less than $300 to more than $750. With some companies, cleaning the equipment was included, whether you wanted it or not. Other companies impose an extra charge for equipment cleaning.

Beware of companies that quote low prices (“$99!”). Most use low “starting” prices as a bait-and-switch tactic.

If you’re worried about specific contaminants (mold, dust), ask companies to inspect the job beforehand and to show you any contamination that would justify duct cleaning. Be very skeptical if a company issues dire warnings about mold, which is usually not found in ductwork. If they suspect mold, ask them to submit the sample to a lab for analysis.

Another red flag: companies that propose applying biocides to kill microorganisms. The EPA cautions against these chemicals. While some are approved for duct cleaning, the chemicals themselves can be irritants. If you choose to do this during duct cleaning, ask the company to present evidence that the chemical has been approved for use in duct-cleaning applications; it should have the EPA data sheet for the chemical on hand. Note: Biocides should never be applied to fiberglass-lined ductwork.

Confirm that any cleaning will cover the entire system, including supply ductwork, return ductwork, supply plenum (chamber), return plenum, and all registers and grilles. You may agree, for a reduced price, to exclude the blower-fan assembly, heat exchangers, evaporator coils, and collector pans—if those are serviced under a maintenance plan with a heating and air-conditioning contractor. But these are the elements most relevant to system efficiency and should be explicitly listed by the duct-cleaning company, unless you have agreed to exclude them.

Before agreeing to any work, get written estimates after each inspection.

Have the company agree in writing that it will perform the following:

• Open or create access ports or doors to allow the entire system to be cleaned and inspected.
• Inspect the system before cleaning to make sure there are no asbestos-containing materials. (Asbestos-containing materials should be disturbed or removed only by specially trained and equipped contractors.)
• Follow NADCA guidelines in attaching some sort of vacuum device to the system during cleaning to remove loosened particles.
• Use vacuum equipment that exhausts particles outside of the home or, if the vacuum exhausts inside the home, use only vacuuming equipment with high-efficiency particulate air (HEPA) filters.
• Protect carpet and household furnishings during cleaning.
• Use well-controlled brushing of duct surfaces in conjunction with contact vacuum cleaning to dislodge dust and other particles.
• Use only soft-bristled brushes for fiberglass duct board and sheet metal ducts lined internally with fiberglass. (Although flex duct can also be cleaned using soft-bristled brushes, it can be more economical to replace accessible flex duct.)
• Take care to protect the ductwork, including sealing and reinsulating any access holes that have been made or used.
• Follow NADCA standards for air-duct cleaning and the North American Insulation Manufacturers Association’s recommended practices for ducts containing fiberglass lining or constructed of fiberglass duct board.