It’s Spring! The sun is shining, there are smiles all around, you turn your air conditioner on, leave the house to go run some joyful errands, and you return to….. Your house smelling like the dirty clothes hamper? Ew!


Don’t be too turned off; this is a common problem that has a name in the Heating and Cooling Industry: ‘Dirty Sock Syndrome.’


 ‘Dirty Sock Syndrome’ : when your air conditioner gives off a moldy, mildew-like, often foul, moldy smell when you turn it on.  


If you notice a change in the aroma of your house when you turn on your air conditioner this Spring, you could be suffering from dirty sock syndrome. But, don’t fear; you don’t have to live in a stinky gymnasium locker room all season- there is a cure!

So, what causes dirty sock syndrome, and is it dangerous to me or my family? 

Dirty sock syndrome  is caused by mold and bacteria that has built up on your evaporator coil. The mold and bacteria are fed and encouraged by the dust that runs through HVAC systems. Dirty sock syndrome often occurs during periods of transition; when an HVAC system has been left dormant for a period of time.  Or, during seasons where heat is needed in the morning, and by noon-time, air conditioning is used. The heat mixed with dust and moisture in the darkness of your air conditioning unit creates the perfect recipe for dirty sock syndrome to develop.  


It is important to prevent mold and to provide good filtration for the air entering your system.  We usually like to think that the air filters we replace every few months are for us, when in fact, they are also for the health of your air conditioner!

If you notice an odd smell, here are a few steps to take before calling your HVAC contractor:

  1. Make sure the drainage pans are empty- if they are full and have standing water or blockages, be sure to clear them.
  2. Check your AC filter; if it is moist or even worse, wet…. It’s time to replace it!
  3. Clear any drainage lines that may have blockage; some moisture is expected, but excessive moisture is a problem.
  4. IF you’ve checked these preliminary culprits, and you still are experiencing a foul odor, then it’s time to call your local HVAC technician. 


So, is Dirty Sock Syndrome dangerous?  It depends.  

Usually the answer is: NO. The variety of bacteria and mildews that cause Dirty Sock Syndrome are not harmful under normal circumstances (a person with a healthy immune system)  If left unattended, the bacteria and mildew can turn into mold, and when mold is left to grow and fester, it can become a health hazard for those living in the home.

Don’t jump off the deep end just yet; just because you have Dirty Sock Syndrome does not mean you have mold! Using a professional HVAC company is the right choice; they’ll open up your system and see what you’re dealing with. 


Replacing your air filter regularly is key to preventing dust and allergens from collecting on the evaporating coils of the AC unit. Another, more intense, way to  prevent mold and bacteria from growing on your cooling coils is to use a UV air purifier.  These air purifiers are used in medical facilities and they quickly kill bacteria and mold and their spores.


Your HVAC technician will clean your evaporator coils to remove any build-up; and that might do the trick, but it’s not a 100% guarantee that it will eliminate your ‘Dirty Sock Syndrome.’ Depending on the age of your AC unit, it may need replacement evaporator coils or, it might be time to replace your entire unit. 


River View Heating and Cooling is here to walk you through solving ‘Dirty Sock Syndrome.’ We’re industry experts who are trained in both preventative measure as well as complete overhauls to rid your house of this syndrome. Give us a call today to schedule a diagnostic appointment.

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