Customer Knowledge Base | Direct Service, Construction & Design Support Center

Contact Us

HVAC Dirty Sock Syndrome Explained

Yes, this is a real thing and verifiable trade terminology.  As the title of the this article implies, this is not something you want to be experiencing or looking up on the internet for that matter.  Dirty Sock Syndrome (DSS) refers to a foul-smelling, mold or mildew-like odor that comes from your air conditioner when you first turn it on. This happens when moisture, dust, and dirt build up on your AC system's evaporator coil, inviting bacteria and mold and creating the ideal environment for them to multiply.

Can Dirty Sock Syndrome make you sick?

Dirty Sock Syndrome can pose health risks if mold occurs in the air conditioning unit and starts to develop uncontrollably.  The effects largely will depend on the type of mold and severity of the mold, but mold exposure can cause:

These effects can range from mild to severe, but those with severe allergies, asthma, or have respiratory problems will likely the suffer most.

Often, DSS will go away on its own with some time and usually only rears its ugly head when seasonal usage begins for the first time.  If the problem persist, here are some treatments we recommend: 

  • Clean your evaporator coil(s).  Read more.
  • Perform routine preventative maintenance on your HVAC system. During PM visits, the conditions that create DSS are monitored and mitigated with cleaning recommendations, algae treatments and drain line maintenance.  Read more.
  • Clean your ducting.  This one is a bit extreme but in some rare cases, excessively dirty ducting could be preventing the dissipation of this foul odor. 
  • An Ultraviolet (UV-C) Air Treatment System kills a high percentage of airborne bacteria and surface mold passing by the light, and can help to eliminate "Dirty Sock Syndrome"

This article has been shared by Direct Service, Construction and Design to specifically accommodate our intended clientele.  The intent of sharing this information is to better inform the public of these general topics, expand knowledge and safety for all and provide crucial information in regard to their MEP and building systems and/or assets. It is NOT our recommendation that any article recommendations or how-to scenarios be attempted by anyone other than a qualified or competent person.