Dirty Sock Syndrome: Causes and Solutions

Dirty Sock Syndrome sounds made-up, doesn’t it? It could just as easily be a term for a smelly collegiate dorm room.

It’s a legitimate problem in HVAC, though, and it’s a term that’s been used by both HVAC industry professionals and homeowners for decades. Normally in an article like this we’d tell you what the technical, industry definition of the problem is, except that dirty sock syndrome is the official definition.

If you’ve ever noticed a musty smell in your home, or similar unpleasant odors, this could very well be the cause and you might not realize it.

That’s why we’re here to help; educating people on the problems that could affect their HVAC system is the best preventative measure to ensure you stay comfortable in your home. So we’ll help you identify if you have dirty sock syndrome, how to remove it if you do, and how to prevent it from ever occurring.

Here in Sacramento, humidity levels get really high, and that can cause dirty sock syndrome if you’re not careful. Regardless of where you live, though, it’s important to know the causes and solutions to avoid costly and annoying issues in your home.

What is Dirty Sock Syndrome?

Dirty sock syndrome is caused when there’s a buildup of bacteria and mold on the evaporator coil inside your air conditioner or heat pump, creating a musty, dirty sock smell.

This bacteria growth causes the air around it to smell, and the movement of air through your ductwork carries this smell throughout the home.

To be clear, mold and mildew can exist elsewhere in your home and create similar smells. But this refers specifically to the problem within the AC unit.

The reason the evaporator coil is susceptible to this buildup is that, as the name suggests, it’s absorbing moisture to be removed from your home. This is a large function of your air conditioner, and if there are issues with it, buildups of condensation can occur that lead to organic matter spreading.

Does Dirty Sock Syndrome Harm Your Health?

The good news here is that the health implications are usually minor. The bad news is that they can still be annoying and omnipresent in the home, particularly during summer months when the air conditioner is running a lot.

The most common side effects of dirty sock syndrome are respiratory sensitivities. A nagging cough or allergic reaction. Rarely is it something more serious, but it’s also annoying and can affect your quality of life.

If you have pre-existing respiratory issues, though, that could be a different story. 

Does Dirty Sock Syndrome Harm Your AC?

Your air conditioner can continue to run and cool your home with dirty sock syndrome. Indeed, this is the entire reason you smell it when the AC kicks on.

However, the presence of dirty sock syndrome means something is wrong with your air conditioning in the first place. You are losing efficiency in the process and could be at risk for a larger breakdown that would require a costly repair or replacement to fix.

So it’s not worth ignoring.

Is Dirty Sock Syndrome a Problem for Me?

Do you have a musty smell in your home? Does it seem to be tied to the running of your air conditioner or HVAC unit’s fan?

If these things aren’t true, you’re probably safe. The only way to know for sure, though, is to have regularly scheduled tune-ups of your equipment, with the technician checking the evaporator coil for any buildup that may be affecting it.

The Importance of Indoor Air Quality

Dirty sock syndrome relates to a much larger point about the importance of indoor air quality (IAQ).

You spend thousands of hours in your home every year, and the air you breathe in your home directly contributes to your wellbeing.

This can include considering better filters, air purifiers, humidity-controlling products such as whole-home dehumidifiers or humidifiers, and more.

The consequences of ignoring these things can include your system being less efficient, breaking down sooner, and being less comfortable in your home at any time of the year.

ALSO READ: What’s the Ideal Indoor Humidity?

Many of the best practices for avoiding dirty sock syndrome should be practiced by anyone looking to stay happy and healthy in their home.

Preventing Dirty Sock Syndrome

Prevention is better than having to remove buildup once it’s already formed. Here is everything you should be doing:

1. Replace your filter often – a clogged filter can lead to buildup of detritus elsewhere in your system.
2. Use a high-quality air filter – better filters can capture more bacteria and organic particles that can cause problems elsewhere. Aim for MERV 13 or higher in the efficiency of your filter.
3. Consider a thorough ductwork cleaning every 3-5 years – buildup will happen in your ductwork over time regardless of what else you do, and this problem is worse in households with smokers or pets.
4. Invest in a whole-home dehumidifier if you struggle with high humidity – reducing humidity during the hottest months is a good practice anyway, but it also makes it less likely that your system will develop dirty sock syndrome.
5. Invest in a UV Light or other air purifier – UV lights are installed inside your system and kill organic matter that passes through them. This could be bacteria, virus particles, and other nasty contaminants. It can keep your system (and your body!) healthier regardless of whether or not you have dirty sock syndrome.
6. Keep your drain pan clean – routinely having your drain pan inspected and maintained can be an important step in stopping dirty sock syndrome.

Should you be doing all of these things? Potentially. The details will depend on your specific situation. Each one is good advice for many homes, though, regardless of whether or not the HVAC system has dirty sock syndrome.

Removing Musty Smells From Your AC

This is a worse scenario than the one above, once your system already has a problem. Still, it’s fixable.

Some of the same advice applies. You may want to upgrade your filter. You should consider either a dehumidifier in your basement and/or a UV light in your HVAC system.

If there’s a buildup on your evaporator coil, though, the only way to get rid of it is to have a licensed technician come to your home and thoroughly wash and treat your coil. This goes beyond what is often done in a typical tune-up, but can be done as part of a tune-up as well, depending on the company’s policy.

Once this step is done, it’s important to realize why it happened, which likely relates to the items we mentioned above like dirty filters or high humidity. Identifying the problem and fixing it is necessary to avoid repeating the problem.

Will It Go Away On Its Own?

It’s unlikely that mold or mildew in your HVAC system will go away on its own. The best you can hope for is that it won’t get any worse, and the problems will remain limited to bad smells and occasional respiratory irritants.

Ignoring problems generally doesn’t help, and this is no exception.

What Else Could be Causing Smells in My Home?

Dirty sock syndrome, and the specific buildup of organic material that leads to it, isn’t the only thing that can cause a smell in your home.

So what else could it be?

We can’t answer this definitively for each household, but here are some common culprits:

1. Faulty equipment
2. Water buildup somewhere in your system
3. Clogged filter
4. Mold or mildew elsewhere in your home
5. Large deposits of dust and debris in your ductwork. Even a great filter won’t prevent this from spreading throughout your home.
6. Plumbing issues (water heater, garbage disposal, toilet, etc.)
7. Faulty sump pump or sewer line backup

There are others we could list; this is only a partial list of possibilities. Some of these are HVAC problems, but many aren’t. Dirty sock syndrome is only one possible cause of a musty smell in your home, but it occurs just as often as anything we just listed above.

Regular maintenance and attention to any smells or abnormalities in the operation of your HVAC is the best way to ensure you aren’t caught off guard and subject to a costly repair bill down the road.

If you’d like to have your system inspected and tuned up, regardless of whether or not it’s producing a musty smell, CABS HVAC has trained and licensed technicians who can walk through all the potential problems in your system to make sure you have none of them. Reach out to us today!