Dirty Sock Syndrome in high efficiency HVAC units

I was recently told my new HE HVAC unit has the dreaded dirty sock syndrome.  Never had this problem with the old unit.  My research shows me it is usually tied to heat pumps.  I have a gas furnace.  Research shows mixed opinions on solutions: UV lights, treated coils, etc.  I do not want to fork out any more money if it's not going to fix the problem.  I was also advised to run the A/C with the windows open to clear out the smell.  I did this and it did not work (and now I feel guilty for wasting energy all day).  I was told there is no health threat associated with DSS.  How is this not possible?  I have a 9-month baby in the house and am concerned.  What are my options?  And am I responsible financially for the fix (if there is a fix)?  

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Dirty Sock Syndrome is actually caused by a combination of bacterial "slime" (biofilm) and mold, such as yeasts, that typically grow on the coils of the unit.  The biofilm has been described as being like the slippery, slimy surface that develops inside a pet's water bowl. I think you would agree that is not significantly hazardous either.

I have tested for it (mainly mold) in several instances and have read similar accounts.  Essentially the mold spores do not easily become airborne, perhaps because they grow in the slime, nor are yeasts generally considered particularly hazardous.  Therefore it is rare to even detect the mold in air samples.  The bacteria is also not of a concern other than the odor it creates.  Unfortunately I have not read of any surefire long-term remediation method either.

Thanks Bob.  Glad to read your thoughts on the low health risks associated with DSS.  

I had a customer who came to me about DSS.  She had been looking for an answer for several years, after trying ultraviolet lights, filters, bleach, etc.  The smell only occurred in the fall, after the cooling season.  I found some flex duct returns that had a low spot where moisture accumulated and didn't drain. In any case, she had the ducting removed entirely, replaced with steel ducts, and the DSS disappeared.

Thanks Andrew, but I'm not sure I'm ready to go this route.  It seems like I would have experienced DSS with my previous unit if the problem is in the ducts.  

Your mention of the low spot in the flex ducting collecting water (thereby soaking the insulation at some point, most likely) makes me wonder if internal duct lining may contribute to DSS. The OP is puzzled by his DSS in that he's running a gas furnace instead of a heat pump, where DSS problems are commonly reported.

That your customer had her ducting replaced with steel ducts, and with the assumption said ducts were externally insulated vs. internally insulated, makes me think internal lining of ducts remains not to be a good idea.

Was the AC coil and drip pan checked for mold?  That would be the easiest fix.

No, actually the service tech gave me his diagnosis just by asking me questions.  We have since called the dealer back and they are sending someone else out to further assess the situation.  I will definitely make sure they check the coil and drip pan for mold.  The gentleman on the phone said they may need to order us a new coil.  

I'm still perplexed as to why this is happening since we have a gas furnace and all my research ties DSS to heat pumps.  Research has also shown that DSS is common with high efficiency units.  Any thoughts as to why?   

 I would keep good tabs on effects on your baby as a first priority.  Coils can be cleaned, they don't have to be thrown away when dirty.  Has your heat run since the furnace was installed?  You stated that you ran the AC but didn't mention the heat.  My GUESS as to the reason for the problem with heat pumps is that they generate a low temperature heat vs. a gas furnace, and the higher temperatures of the gas furnace may kill mold spores on the coil.  If the heat hasn't run, try it.

Thanks Stan. I am still very concerned about the effects on my baby... almost to the point where I don't want to run the A/C until this problem gets resolved.  Seeing how we live in Texas, this could be challenging.  

And to answer your question... we have been using the gas furnace all winter, which is why I don't understand why we're experiencing DSS.  We've had a few warm spells this January and have turned on the A/C, which is when we notice the smell.  Is it possible that it's the high efficiency of the gas furnace that's preventing the temperatures from getting hot enough to kill the mold spores?  

There is a cure for Dirty Sock Syndrome.  You may not find long lasting results with chemicals, and UV light may not be effective.  A deposit of an antibacterial must be left on the coil, or it will eventually come back each time the coil gets wet.

 

The cure is not expensive or difficult to apply.  What you need is a very dilute solution of pine oil.  See link or search, "Dirty Sock Syndrome" in YouTube:

http://www.youtube.com/watch?v=VclGuogRPCY

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