You know it's time for your laundry to spend a little one-on-one time with the washing machine when your hamper smells like a football locker room. When the aroma overtakes your home every time you turn on the air conditioner, however, it may be more than just your laundry that needs cleaning.

Dirty sock syndrome is real, and it's a surprisingly common problem suffered by homeowners, especially among heat-pump owners who alternate between heating and cooling mode throughout the early spring. If your home's starting to take on that post-game aroma, then you'll want to know how to treat your musty HVAC system and make your home smell fresh again.

What Causes Dirty Sock Syndrome?

Springtime along the Wasatch Front can quickly alternate between warm sunshine and bitter cold. This makes the use of both heating and cooling modes on your heat pump a necessity in most cases. But the combination of a constantly damp air handler and coil temperatures that are rarely hot enough to sterilize most microbial life can set the stage for explosive mold and bacteria growth in your HVAC system.

Dirty sock syndrome is usually caused by a broad range of mold and bacteria growths, primarily on the evaporator coil and other damp surfaces of your HVAC system. Once mold and mildew builds up on your evaporator coil, the passing air can carry with it a tell-tale moldy, musty odor that's often blamed on dirty clothes or garbage.

Is It Dangerous?

When it comes to your HVAC system's overall performance and your home's indoor air quality, dirty sock syndrome is definitely a concern. However, the condition is not a life-threatening issue. Most molds associated with dirty sock syndrome are only mildly toxic to most people, with coughing, sneezing, and minor respiratory symptoms being typical symptoms.

If you have young children, elderly adults, or people suffering from compromised immune systems in your home, however, you'll need to address dirty sock syndrome as soon as possible.

How Can It Be Treated?

To deal with dirty sock syndrome, you'll need to thoroughly clean your HVAC system's evaporator coil as well as the condensate drip tray located directly below the coil. There are a couple of ways you can safely and successfully clean your evaporator coil:

  • Mix one cup of bleach with a gallon of water in bucket. You can also add a few drops of mild dishwashing detergent to boost your cleaning solution's effectiveness. Use a soft-bristled brush to carefully clean the entire evaporator coil. After scrubbing the coil, use distilled water to rinse it off.
  • Take a can of foaming no-rinse coil cleaner and spray it on the entire coil. As the foam works through the mold and debris, the solution will break apart and drain away, taking the debris with it. Repeat the application process as needed.
After cleaning the evaporator coil, you should also clean and disinfect the condensate drip tray. Also make sure that there aren't any clogs or other obstructions preventing the drip tray from draining properly.

Can It Be Prevented?

No one wants to see or smell dirty sock syndrome making an all-star comeback. Fortunately, there are several steps you can take to keep your HVAC system from turning moldy and musty:

  • Regularly change your HVAC system's air filter. This step is absolutely vital, as a clogged air filter can allow mold, bacteria and debris to infiltrate your HVAC system. Replacing your air filter at least every three months is usually enough to prevent those problems from happening.
  • Consider upgrading your air filter. In addition to regular air filter changes, you should also consider stepping up to an air filter that offers more effective filtration. For instance, upgrading from a fiberglass air filter to one that uses pleated paper media can improve your HVAC system's overall effectiveness while boosting your home's indoor air quality.
  • Have your HVAC technician perform regular checkups on your HVAC system. A regularly scheduled inspection performed by your technician can help prevent dirty sock syndrome and other problems before they have a chance to start.
  • Invest in an ultraviolet (UV) germicidal lamp system. UV-C light has been scientifically proven to curtail bacteria, virus, and mold growth thanks to its unique germicidal properties. Surrounding your evaporator coil with one or more UV lamps can potentially keep mold and bacteria from growing on the coil and surrounding areas.
  • Have your HVAC technician apply a special coating to the coil. Antibacterial coatings are proving effective at preventing mold and bacteria growth on evaporator coils.


If you need help tackling dirty sock syndrome or any other HVAC issue, Hartman Heating, Air and Fireplaces can help. Don't hesitate to contact usthrough our online form.