Mold: A Common HVAC Complaint That Is Easy To Deal With

Mold Removal HVACThis post sponsored by BBJ Environmental, your source for mold and mildew remediation products.

The presence of mold in an HVAC system is a common complaint.  Mold is a sneaky little bugger.  It can grow and proliferate and make building occupants sick without ever being seen.   And the fastest way to spread mold through a building is through a forced-air HVAC system.

The reason this complaint is so common is that mold is always present in your buildings and your HVAC system to the extent that it is present in your building’s environment.   There will be more mold in humid weather and less in dry weather.   You will never get rid of it completely, but you can control it.   All it needs to grow is moisture and food.   Take those away and the mold goes away.

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According to the U.S. EPA, you should routinely inspect your HVAC systems, not just for mold, but for moisture.   Look at drain and condensate pans to make sure they are draining properly.   If they are plugged, the moisture that accumulates will become a mold factory.  Also make sure that all HVAC ducts and system components such as air handlers, blowers, plenums and the like are free of any moisture.

If, despite regularly inspecting your system, you are still getting complaints about it (mold starts to grow in as little as 48 hours), here are some tips you can share with your HVAC contractor for cleaning it up:

1.) Turn off your HVAC system.

2.) Everyone involved in this cleaning should wear at least an N-95 respirator

3.) Replace anything porous, such as filters or insulation that has become wet.  Double-bag the waste using at 6-mil or thicker plastic bags.

4.) Use wet vacuums to clean out any standing water.

5.) Use an EPA registered disinfectant labelled for HVAC use to clean non porous surfaces (Duct work, coils, plenums, pans, etc) of mold, mildew and other dirt. BBJ MMR-II ready-to-use disinfectant and mold cleaner will kill and remove mold, mildew and odor causing bacteria.

6.) As an added measure, isolate each section of ductwork you clean with bladders so the spores you stir up during cleaning don’t spread to other parts of the system or the building. Fog the area with an EPA registered disinfectant.

7.) Apply a mold and mildew inhibitor to all components of the HVAC systems. Again, this must be EPA registered and specifically labelled for use in HVAC systems to limit risks associated with using the wrong chemicals and cleaners in HVAC systems. Goodway’s CoilShine-BC is EPA registered for use in HVAC systems to control mold growth for up to 2 years.

8.) As a final step, HEPA vacuum anything that you cleaned up.

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20 comments


  • I am a heating contractor in Chicago Illinois and I run into this problem a lot in the hot muggy summers here. this is a lot of good information for the remediation of mold but it seems like a lot of these things listed are a bit above what a homeowner is capable of. Unless you have some sort of hands on mechanical experience you will not be able to accomplish such things like checking the condensate pan and checking the ductwork for moisture. This seems good checklist for a flood type situation with minimal water damage. One thing that I wnated to add where I see a problem is in humidifier pads. These pads rarely get changed by the homeowner, when they need to be changed every season. What I find is that these pads get so moldy that you actually start to get bad odors in the home and not know where they come from. I recommend that homeowners should change these pads each season and wash out the holding tray for the pad with bleach and water. Also check the drain hose and inspect for mold, i am always surprised by how much they get colgged up and filled with mold. These are some Humidifier Tips that I give my Chicago customers and I find it gives good results.

    November 12, 2009
  • Goodway Blogging Team

    Mr. Gremillion raises an excellent point. Our primary audience at Just Venting consists of HVAC industry professionals. As he pointed out, a professional contractor would have knowledge and experience that we wouldn’t expect a homeowner to have. Areas such as humidifier pads and condensate pans aren’t something you would expect a homeowner to think about it or attempt to clean.

    This might actually be an opportunity in disguise. Consider talking about it with your customers — residential AND commercial, when you go on service calls. Maybe you can even design a basic maintenance or “mold prevention” program to sell them, much like the pre-season furnace checkup offers you see before a freezing cold Illinois winter rolls in.

    Rich Silverman
    Goodway Blogging Team

    November 12, 2009
  • Len Douglas

    can fluorescent lighting be used to treat mold in air handler and can it be self installed where can these be located my hvac co. wants to install for 1200.00! thanks

    January 13, 2011
  • Tim

    I’ll defer to your HVAC pro on this one. If you’ve got mold problems, then there are a variety of solutions, including biocides and yes, “newer” light based technologies. If you’re not comfortable with the quote, contact a few different installers and ask them for their input. Might be surprised at the options.

    May 5, 2011
  • […] water combined with dust and dirt within your ductwork create a breeding ground for spores to grow. Take immediate action with these […]

    May 7, 2013
  • A mold treatmen expert ought to be hirted at the
    first signs of mold. When this takes effect it’ll produce spores into the air.

    The Dupli-Color TV video is inspirational.

    December 15, 2013
  • But besides cost benefits, you have to find an LPG provider that offers exemplary
    service. Therefore, early diagnoosis and treatment is essential for a healthier home.
    Firstly, clean annd identify any infected places.

    December 16, 2013
  • […] may form condensation, proving to be the perfect breeding ground for fungi and mold to develop. Molds can be easily carried in through dust particles and their spores pose a danger to your health if they are inhaled. […]

    June 23, 2016
  • vernon kingery

    How valuable is an uv light 1002 system in an
    3500 home ac? Do you really need it? Also
    should I put storm surgers on it? What Is normal cost of buying and install? How much should a home duct system special plastic black insulated polymer made for outdoor weather and heat cost? Approx. 40ft.

    July 28, 2016
  • A mold treatment expert ought to be hired at the
    first signs of mold.

    October 30, 2016
  • John

    I live on the coast of North Carolina where it’s very humid doing the late spring , all summer and early fall !
    The AC guy told me that He could installed a light would omit the mold forever . The labor and material would cost $350 to omit the mold ! I was wondering IF anything else out there to omit mold !

    November 3, 2016
  • A proper maintenance can prevent molds like this. It’s much better to prevent.

    November 12, 2016
  • Lisa

    I have a question… i live in an apartment and staying sick.. all i smell is mold mildew… apartment is only 2 yrs old…
    Question.. my ac/heating unit is always sprayed with the sprinklers.. would this be an issue??

    November 28, 2016
  • Unfortunately we see this often here in St Louis because of our super humid summers. Families get sick and are in the hospital for breathing problems and little do they know its simply their AC at their house causing the problems. Just do regular maintenance to the system and everything should be good for the most part.

    December 2, 2016
  • sandy garbrandt

    we just purchased a new house only 3 years old and its out summer house so were not always there ,but I got really bad allergies thought it was a cold but my husband says he smells something in the house and he has a headache and nausiuos,we r in a panic what should we do?

    January 4, 2017
  • Tim

    We would suggest contacting a certified contractor who handles mold and mold remediation in your area to have them come out and completely check the house.

    February 2, 2017
  • Tim

    If you are referencing your outside unit, the answer would be no. I would contact a licensed HVAC contractor to check your air handler(s). a good cleaning may be all they need, but they would be able to diagnose other problems.

    February 2, 2017
  • Tim

    He’s probably referring to a UV light system, many of which have shown to help with mold issues. However, the best way is to make sure that the system is properly maintained, often.

    February 2, 2017
  • Chris

    I paid about 2k two months ago to a duct cleaning company for green mold removal from my hvac coils and pads inside the unit and all 20 vents with antimicrobial chemicals. Required two visits and staying out of the house for several hours each time. Had a mold inspector in yesterday and there’s mold again in the unit and dirt in the vents. Humidity in the house usually in upper 50% range, as high as 70%, never lower than about 40% Aside from what may have been shoddy service by the duct cleaning company, I am wondering if a hvac dehumidifier might work to reduce humidity in the hvac unit and house. I have a Lennox system, one inside and the other fan outside the hous . Not much knowledge on all this but I know I have to reduce humidity to keep mold away. Any ideas???

    February 7, 2017
  • Dwight Stewart

    I am looking to clean my blower coils on the AC and disinfect the whole system and have the Plenum Box Mold controlled. What could this cost me? Can you respond quickly – thank you.

    February 15, 2017

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