Moisture can enter the duct system through leaks or if the system has been improperly installed or serviced. Research suggests that condensation (which occurs when a surface temperature is lower than the dew point temperature of the surrounding air) on or near cooling coils of air conditioning units is a major factor in moisture contamination of the system. The presence of condensation or high relative humidity is an important indicator of the potential for mold growth on any type of duct. Controlling moisture can often be difficult, but here are some steps you can take:

The EPA and CMHC researchers used different methodologies. The CMHC study called on several 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. The EPA study prescribed and controlled methods used on a smaller number of homes. While the duct-cleaning industry argues both studies have flaws, no other research has challenged the findings. And although the equipment and methods used by duct-cleaning companies have changed since these studies were conducted, the air ducts in homes haven’t.

3/8/2019Thank you for your feedback.  Yes, we were late, and we apologize for that.  Sometimes things happen, unfortunately.  However, it was not no show, no call.  There was a technician in your home today.  He began to take the vents off.  You advised him since they were behind schedule, he would have to leave and the service could not be completed.  He then put the vents on and left.


If you think duct cleaning might be a good idea for your home, but you are not sure, talk to a professional. The company that services your heating and cooling system may be a good source of advice. You may also want to contact professional duct cleaning service providers and ask them about the services they provide. Remember, they are trying to sell you a service, so ask questions and insist on complete and knowledgeable answers.
Pay particular attention to cooling coils, which are designed to remove water from the air and can be a major source of moisture contamination of the system that can lead to mold growth. Make sure the condensate pan drains properly. The presence of substantial standing water and/or debris indicates a problem requiring immediate attention. Check any insulation near cooling coils for wet spots.
Duct cleaning generally refers to the cleaning of various heating and cooling system components of forced air systems, including the supply and return air ducts and registers, grilles and diffusers, heat exchangers heating and cooling coils, condensate drain pans (drip pans), fan motor and fan housing, and the air handling unit housing (See diagram).
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