The Home Inspector's Guide to Air Duct Cleaning, Part 4: Helping a Homeowner Choose a Duct Cleaning Service Provider

by Nick Gromicko, CMI® and Ben Gromicko

To find companies that provide duct cleaning services, a homeowner should go online or contact the National Air Duct Cleaners Association (NADCA). Homeowners should not assume that all duct cleaning service providers are equally knowledgeable and responsible. They should talk to at least three different service providers and get estimates before deciding whether to have their ducts cleaned. When the service providers come to the house, the homeowner should ask them to show them evidence of contamination that would justify having the ducts cleaned.

The following tips should be factored into the homeowner's decision-making process about whether to get their HVAC system's ductwork cleaned:

  • Duct cleaners who make sweeping claims about the health benefits of duct cleaning should not be hired because such claims are unsubstantiated. Homeowners should not hire duct cleaners who recommend duct cleaning as a routine part of their heating and cooling system's maintenance.

  • The homeowner should not allow the use of chemical biocides or chemical treatments unless they fully understand the pros and the cons.

  • The homeowner should check the company's references and customer reviews to be sure other customers were satisfied and did not experience any problems with their heating and cooling system after cleaning.

  • The homeowner should interview potential service providers to ensure that:

    • they are experienced in duct cleaning and have worked on systems like theirs; and

    • they will use procedures to protect the occupants, their pets, and the living space of their home from contamination.

  • The homeowner should ask the service provider whether they hold any relevant state licenses. Some states may require air duct cleaners to hold special licenses.

  • The homeowner should make sure that the duct cleaner they choose will provide a written agreement that outlines the total cost and the scope of the job before work begins.


What to Expect from an Air Duct Cleaning Service Provider

If a homeowner chooses to have their ducts cleaned, the service provider should:

  • use measures to protect the home's carpeting and household furnishings during the cleaning process;

  • open access ports or doors to allow the entire system to be inspected and cleaned;

  • inspect the system before cleaning to ensure that there are no asbestos-containing materials in the heating and cooling system. Asbestos-containing materials require specialized procedures for removal and should not be disturbed or removed except by specially trained, certified and equipped contractors;

  • have vacuum equipment that uses high-efficiency particle air (HEPA) filters, and exhausts the particles to the outdoors;

  • use well-controlled brushing of duct surfaces in conjunction with contact vacuum cleaning to dislodge dust and other particles;

  • use only soft-bristle brushes for fiberglass duct board and sheet metal ducts internally lined with fiberglass. Although flex duct can also be cleaned using soft-bristle brushes, it may be more economical to simply replace the accessible flex duct; and

  • take care to protect the ductwork, including sealing and re-insulating any access holes that the service provider may have made or used so they are airtight.

How to Determine Whether the Duct Cleaner Did a Thorough Job

A thorough visual inspection is the best way to verify the cleanliness of a heating and cooling system. Some service providers use remote photography and scope cameras to document the condition inside the ducts. All portions of the system should be clean; no debris should be detectable with the naked eye. 

The Post-Duct Cleaning Consumer Checklist below should be shown to the service provider before the work begins. After completing the job, the service provider should be asked to show the homeowner each component of the system to verify that the job was performed satisfactorily.

If a homeowner answers "no" to any of the questions on the checklist, it may indicate a problem with the job. The service provider should be asked to correct any deficiencies until "yes" can be answered to all the questions on the checklist.


Post-Duct Cleaning Consumer Checklist




Did the service provider obtain access to and clean the entire heating and cooling system, including ductwork and all components (drain pans, humidifiers, coils and fans)?

Has the service provider adequately demonstrated that the ductwork and plenums are clean? (The plenum is the space where supply or return air is mixed or moves; can be duct, joist space, attic, crawlspace, and/or wall cavity.)


Is the heat exchanger surface visibly clean?



Are both sides of the cooling coil visibly clean?

If you point a flashlight into the cooling coil, does light shine through to the other side? (It should if the coil is clean.)

Are the coil fins straight and evenly spaced (as opposed to being bent over or smashed together)?

Is the coil drain pan completely clean and draining properly?


Are the blower blades clean and free of oil and debris?

Is the blower compartment free of visible dust and debris?


Is the return-air plenum free of visible dust and debris?

Do the filters fit properly, and are they the appropriate efficiency, as recommended by HVAC system's manufacturer?

Is the supply-air plenum (directly downstream of the air handling unit) free of moisture stains and contaminants?

Metal Ducts

Are interior ductwork surfaces free of visible debris? (Select several sites at random in both the return and supply sides of the system.)


Is all fiberglass material in good condition (i.e., free of tears and abrasions, and well-adhered to underlying materials)?

Access Doors

Are newly installed access doors in sheet metal ducts attached with more than just duct tape (e.g., screws, rivets, mastic, etc.)?

With the system running, is air leakage through access doors or covers very slight or non-existent?

Air Vents 

Have all registers, grilles and diffusers been firmly re-attached to the walls, floors and/or ceilings?

Are the registers, grilles and diffusers visibly clean?



Does the system function properly in both the heating and cooling modes after cleaning?


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