The leading causes behind mold growth inside HVAC equipment are:


High humidity levels in your home are the biggest cause of mold growth inside the HVAC system as well as inside the house itself. Summer months are usually the time when natural humidity is at its highest, though moisture issues exist in the home year-round. This includes excess humidity caused by showers and baths, washing machines, and other appliances


Thermodynamics is tricky, but condensation is common.  While some of us might not understand how it happens, we can all be victims of the results of condensation in your ducts and your main unit.

The cooling process that your HVAC system goes through each day produces condensation. Normally, this excess moisture is moved away from the system through the condensate pan. However, clogs or other issues can prevent proper draining.

Clogged condensate lines create standing water. Standing water creates mold.

Poor Ventilation: 

If your home is poorly vented, it causes pockets of stagnant moist air to form indoors. Any steam or evaporating water in your air creates more humidity that cannot be circulated out because of poor ventilation. These issues often arise when bathroom exhaust fans and range hoods are not properly used or have malfunctioned.

How to Prevent Mold Growth in Your HVAC System

Steps to Remove Mold from Heating and AC System

If you are looking at the moldy spots near your vents with frustration, here is how you can channel that rage toward tackling that nasty infestation.

First, remember that mold can be dangerous. You need to don the proper PPE when handling mold problems.

This means:

  • An N95 mask
  • Industrial grade gloves
  • Safety goggles

You may even want to invest in a painter’s suit that you can dispose of after finishing. Next come the tools of the trade. Keep in mind: whatever you use to clean mold, you will need to throw it away. If you don’t, you could be inviting mold right back into your home.

You will want a soft brush and some rags to do the dirty work. You can use a few cleaning solutions to tackle mold. The first is a home remedy.


  • One tablespoon household detergent (dish soap or detergent)
  • Half tablespoon baking soda
  • One cup water

If you are dealing with severe mold growth, consider using an EPA-approved mold detergent.

Now, onto the actual cleaning process:

  1. Turn off your HVAC system and make sure all the heating/cooling vents are not pushing air.
  2. Start by spraying moldy areas with cleaner and scrubbing gently with a brush or rag.
  3. Repeat until you’ve reached all the spots where visible mold is present.
  4. Dispose of all rags and PPE in trash bags and immediately take them outside.

The last step is important. All your hard work goes right down the drain if you let the spores come right back. Proper disposal ensures that the mold is far away from your home.


Comments are disabled.