Duct cleaning has not been shown to prevent health problems and studies haven't conclusively demonstrated that dust levels in the home decrease because of dirty air ducts, according to the EPA. This is because much of the dirt in air ducts adheres to duct surfaces and may not enter the living space. Dirty air ducts are only one of many possible sources of air particles in homes. Pollutants enter from outdoor and indoor activities, such as cooking or smoking.
You should consider having the air ducts in your home cleaned if:
- There is substantial visible mold growth inside sheet metal ducts or on other components of your heating and cooling system.
- Ask the service provider to show you any mold. Whether a substance is mold can only be determined by an expert and may require laboratory analysis for confirmation
- You have insulated air ducts and the insulation gets wet or moldy. It cannot be effectively cleaned and should be removed and replaced. Mold will return if the conditions causing its growth are not corrected.
- Ducts are infested with vermin such as rodents or insects.
- Ducts are clogged with excessive amounts of dust and debris.
Who should I hire to clean my ducts?
The EPA suggests the following:
- Get estimates from at least three service providers.
- Check references.
- Ask whether the service provider holds any relevant state licenses. As of 1996, the following states require air duct cleaners to hold special licenses: Arizona, Arkansas, California, Florida, Georgia, Michigan and Texas. Other states may also require licenses.
- Insist that the service provider give knowledgeable and complete answers to your questions.
- Find out whether your ducts are made of sheet metal, flex duct, or constructed of fiber glass duct board or lined with fiber glass since the methods of cleaning vary depending on duct type. A combination of these elements may be present.
- Make sure the service provider follows the National Air Duct Cleaning Association's standards and, if the ducts are constructed of flex duct, duct board, or lined with fiber glass, the guidelines of the North American Insulation Manufacturers Association.
- Commit to a preventive maintenance program of yearly inspections of your heating and cooling system, regular filter changes, and steps to prevent moisture contamination.
How to determine if the duct cleaner did a thorough job
A thorough visual inspection is the best way to verify the cleanliness of ducts. Some service providers use remote photography to document conditions inside ducts. Show the contractor this post-cleaning consumer checklist from the EPA before the work begins. After completing the job, make sure the listed items were performed.
- 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 duct work and plenums are clean? (Plenum is a space in which supply or return air is mixed or moves; can be duct, joist space, attic and crawl spaces, 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 the other side? It should if the coil is clean.
- Are the coil fins straight and evenly spaced (as opposed to being bent over and 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 or debris?
- Is the return air plenum free of visible dust or debris?
- Do filters fit properly and are they the proper efficiency as recommended by HVAC system manufacturer?
- Is the supply air plenum (directly downstream of the air handling unit) free of moisture stains and contaminants?
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 fiber glass material in good condition (i.e., free of tears and abrasions; well adhered to underlying materials)?
- 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?
- Have all registers, grilles, and diffusers been firmly reattached 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?