Was rearranging some ductwork in my basement, and noticed that the stuff I took down was pretty filthy inside (especially the return air ducts).

Is it worthwhile to have ductwork cleaned out? What kind of (if any) efficiency benefits do you get out of it?

  • 6
    And how often should ducts be cleaned?
    – gregmac
    Commented Jul 23, 2010 at 22:17

6 Answers 6


It's not the efficiency which you get -- it's less dust in the air. Less dust equals better health in the long run.

Lots of dust in the ducts is an indication of a bad air filter and/or leaks around the filter or in places where ducts join/turn. I'd look for that as well.

  • I was under the impression that it was also more efficient (less air resistance in the ductwork). Is that not the case? Commented Jul 23, 2010 at 22:29
  • well, if the dust accumulation is high enough (e.g. dust occuping 10-20% of the ductwork space), it might be. But at these levels the ducts become a load hazard, as in too heavy to be supported by the walls :)
    – Rom
    Commented Jul 23, 2010 at 22:54
  • I haven't seen ductwork held up by walls. Usually it is flexible material in homes that is snaked around in the attic. It is fairly lightweight. Commented Jul 29, 2010 at 11:35

Here are the EPA guidelines for duct cleaning and when it is necessary: Should You Have the Air Ducts in Your Home Cleaned?

Keep in mind that the airflow ducts usually aren't as bad as commercials would have you believe, unless the system was run without an air filter. The filter usually sits in your air return, which makes sure any air flowing into your supply ducts is "clean".

So, if you see a lot of crap in your supply ducts, you probably have unfiltered air entering the system (hole in a duct maybe). The other way stuff gets into the supply ducts is from people dropping crap into the floor registers. If it's dirt in the registers, you can usually get it out by lifting the register and sticking your vacuum cleaner's hose in there. Just be careful that you don't gouge or hit the sides of the ducts, which can damage them (they can shed fiberglass).

You may have stuff in your return ducts (animal dander, etc), but because of the air filter, this usually doesn't affect the overall air quality in the house much. The exception would be if you have something in the ducts that the air filter won't trap (mold spores, smelly things).


For me it was. The house I live in now was previously owned by animal owners. I'm allergic to animals and there was a ton of junk in the air ducts so the cleaning got rid of a lot of junk in the air.


Depending on your location mold build-up (in addition to the dust mentioned by others), can be a big reason to clean the ducts. Areas with high humidity can grow impressive mold collections, particularly on systems that have humidifiers as well.


Duct board systems should not be cleaned. They will rip and send more junk into your air. However a metal duct system can be cleaned.

If you use a good filter you should never need to.


The previous owner of my house did some remodeling and did not do a good job of containing the drywall dust. The furnace and ducts were full of it. I had everything cleaned and now there seems to be less dust in the house and the temperature coming out of the duct seems to be warmer for the heat and colder for the air conditioning. I would say it was worthwhile in my case.

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