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A Thorough Duct Cleaning - When You Need It, Who Should Do It?

You may have heard that you can improve the quality of your indoor air and lower your heating and cooling costs through duct cleaning. You may have good reasons to do so, but the U.S. EPA says that no evidence exists yet that cleaning your ducts can actually prevent health problems or that you'll improve your HVAC system's energy efficiency by simply having them cleaned.

Under normal circumstances, ductwork doesn't need cleaning if the HVAC equipment is serviced annually and you routinely clean or change the air filter for the blower. A forced-air system is a closed network. However, if you have ductwork leaks that go unsealed over a period of time, the air passing through the ducts can pull dust and debris from the spaces it passes through, degrading indoor air quality and depositing dust and debris in the ductwork. It also opens the ductwork for insect or vermin infestation.

Circumstances That Meriting Duct Cleaning

The EPA advises that ducts need to be cleaned under these circumstances:

  • Mold is visibly growing inside the ducts. If you or your HVAC technician discover mold inside your ducts, you should consider having them cleaned. However, the technician needs to take a sample of the suspected mold growth and send it to a laboratory that will test it to see if it is mold and what type. Not all mold is toxic; however, if it's black mold, you may want to schedule duct cleaning sooner rather than later. Black mold is the most toxic and it causes varying degrees of respiratory distress. 
  • Excessive dust or debris inside the ducts. Although it's rare, the insulation that's inside some ducts can break free and obstruct the airflow through the ductwork system. Remodeling your home can also deposit excessive amounts of dust in the ducts and running your HVAC equipment without an air filter can deposit excessive dust inside the ducts. 
  • Insects or vermin are inside the ducts. If you hear or see bugs, mice or rats inside the ducts, having them cleaned may be one way to get rid of them. Besides the nuisance factor, they leave waste behind. The only way that creatures can enter the ductwork is through an uncovered supply or return duct or through breaches in the ductwork itself. If the technician has to use repellents, be sure that you take all the precautions the manufacturer recommends.

Who Can Clean Your Ducts?

Your ductwork is a crucial part of your HVAC system and you should only trust it to a licensed HVAC contractor. In order to obtain a license to work as an HVAC technician, the individual needs to complete extensive training and pass a comprehensive test. Every state requires HVAC contractors to be licensed, have insurance and be bonded. In addition, some states like Michigan require non-HVAC contractors to have state-issued licenses to clean ducts. 

The National Air Duct Cleaners Association (NADCA) is the industry association for duct cleaners and it's always a good idea to check with them, either over the phone or online, to see if the company you're considering is a member. You can also ask the company you're interviewing for references from other customers and check with the Better Business Bureau. 

Before you sign a contract with the service provider, get a firm estimate that contains a detailed outline of the steps the company will take to clean the ducts. Be careful about any chemicals or sealants they intend to use and ask them about their safety. You should also be able to get an MSDS (material safety data sheet) for the products to review. 

It's also helpful to choose a qualified contractor who uses remote cameras so that you can be certain that they have the ability to demonstrate the cleaning process and the results once the job is done. Depending on your ductwork configuration, many of its parts will be physically or visually inaccessible to the average person. 

The contractor also needs to verify that the ductwork doesn't contain any asbestos insulation or fibers. Strict federal and state regulations surround disturbing asbestos. If your home was constructed before 1980, there's a possibility it could contain asbestos in the ductwork, albeit small. Asbestos fibers have been proven to cause a type of lung cancer called mesothelioma, one of the most difficult to treat. 

Avoid high pressure tactics from the providers you interview, especially those that say that duct cleaning will dramatically improve your health. The EPA has not established any connection between clean ducts and healthy indoor air. Any duct cleaner who says they have EPA licensing for cleaning ducts is giving you a misrepresentation because the EPA does not license duct cleaning companies. It does, however, grant licenses to HVAC technicians that allow them to handle refrigerants.

What Tasks to Expect

Under most circumstances, duct cleaning involves:

  • Protecting and covering all the furniture and flooring the cleaning process may disturb
  • Opening all the access panels for your ducts
  • Using vacuum equipment that sits outside, so that the dust gathered during the process vents outside, not inside your home. If the service provider uses the equipment indoors, verify that the vacuum has a HEPA (high efficiency particulate air) filter. These trap the smallest particles likely to be found inside your home.
  • Using gentle movements to avoid breaking through the ductwork material. Should breaches happen or be purposeful, the team will carefully seal them with metal panels, mastic or metal tape. Ductwork tape should never be used to reseal any kind of duct. Its adhesive doesn't last long and it won't seal tightly.

How to Assess Results

After the process has been completed, verify that the duct cleaning included these tasks:

  • Did the cleaning project involve a thorough cleaning of all the components of your blower, including the heat exchanger, evaporator coil, blower fan blades and drain pan?
  • If visible, are all the fins inside the evaporator coil straight? Bent fins slow the cooling process when your cooling system runs. You should also be able to see through the evaporator coil when you shine a flashlight through it. 
  • Are all the register vents firmly secured to the wall, ceiling or floor?
  • Does the system operate properly once it's turned back on?
  • Do all rooms in your home have adequate airflow? If not, there could be an accidental ductwork leak somewhere in the supply duct coming to that space.

Keeping the Ducts Clean Afterwards

The two most important aspects of maintaining the cleanliness of your system after duct cleaning are changing the air filter when it's dirty and having your system professionally maintained annually.

  • Professional maintenance involves a thorough cleaning of all the parts and testing the airflow through the blower and the ducts. 
  • If you have rooms where the airflow is weaker than others, you could have a ductwork leak. Not only do ductwork leaks pull debris into the ducts, they can also circulate carbon monoxide in your home if you use any ducted gas appliances.
  • Turn off your HVAC system and seal the registers with plastic and sturdy tape if you're going to create a lot of dust indoors when you're remodeling or building. Sanding and removing carpet generate a lot of indoor dust that can find its way into your ducts, even with the system off.
  • If your home has a central humidifier built into the HVAC system, maintain it properly to prevent mold from forming inside the ductwork. 
  • When the cooling system runs, be sure that the drain pan is clean and the drainpipe is clear so no water collects that could foster mold growth.

If you'd like more information on the benefits of duct cleaning and whether it's needed for your home, contact We provide trusted HVAC services for homeowners in  Chicagoland, southwestern Michigan and northwestern Indiana. 

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