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Dirty Sock Syndrome: Causes & Solutions

Does your home occasionally smell like dirty socks? The smell has a name, and it’s caused by mold and bacteria in your HVAC system, and can be removed and prevented with the right steps.

Dirty Sock Syndrome: Causes & Solutions

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Joshua Rodriguez


July 27th, 2020

You come home from a hard day’s work, fire up the air conditioner, and after a few minutes, your home smells musty, like stale, dirty socks.

What is this? Is it a problem? And what can you do about it?

We’re here to help with each of those questions. The phenomenon is called “Dirty Sock Syndrome,” and it’s caused by mold and bacteria buildup in your air conditioning system.

The name might sound comical, but it’s a real problem for many homeowners. Typically, you’ll first encounter it in the spring when beginning to use your air conditioner. The buildup of moisture, combined with the natural humidity in the home, creates the proper conditions for the problem to occur.

Fortunately, there are ways to solve this. Finding the right solution is just a matter of assessing your existing system and choosing the best ways to prevent it.

Let’s first take a look at the problem itself, and why it’s harmful, to better understand solutions to the problem.

What Is Dirty Sock Syndrome

Dirty Sock Syndrome is caused by the buildup of mold and bacteria on your air conditioner. Specifically, this buildup occurs in the system’s evaporator coil, which is housed in the indoor A/C unit.

Most indoor air conditioner units are located in a home’s basement. Basements are typically cool, damp, and dark. These are the perfect conditions for mold and bacteria growth. While an air conditioner is designed to handle moisture, the internal components, like anything else in the home, can become dirty and accrue dirt and other particles.

For mold and bacteria to accumulate, they need two things: organic material, and moisture. The dust and dirt that is throughout any home, and the particulates collected by HVAC air filters provide plenty of organic materials (remember that most house dust is made of dead skin cells). The other part of the equation, moisture, can be found in most homes, particularly during the most humid times of the year. The result is buildup and smell.

So is this smell harmful? Let’s take a look at that question as we talk about the importance of indoor air quality as a whole.

Sickness from indoor air quality problems

Why Indoor Air Quality Matters

According to the EPA, the average American spends 90% of their life indoors. While moldy smells aren’t likely to cause serious health risks for most, the EPA’s report goes on to say that those who are most susceptible to indoor pollutants are also the most likely to spend even more time indoors.

While the effects generally aren’t life-threatening, they can certainly be debilitating. Effects of air pollutants can include the following:

  • Eye irritation
  • Nose and throat irritation
  • Headaches
  • General fatigue
  • Respiratory illnesses

Mold and bacteria won’t cause each of these for everyone, but the smell is undeniably annoying and noticeable, and the worst cases of it can indeed become health irritants.

As much as the health concerns, if you’re spending anywhere near 90% of your life indoors, it’s worth making sure that that time is as comfortable as possible.

What Are the Risks of Dirty Sock Syndrome

The risks are twofold: to your health and to your HVAC system. A stinky system is indicative of other problems, ones that could affect the performance and longevity of your system.

To assess the risks, we also have to look at some of the underlying causes of Dirty Sock Syndrome. Because it doesn’t just occur out of the blue, but usually has things leading up to the smell that you notice when you start the system.

One obvious area of potential concern is your filtration. How long has it been since you changed your filter? And what quality of filter is in there? A good filter will catch a lot of bacteria and mold spores, preventing its spread. However, that same good filter will cease to function properly if you go too long without replacing it.

I bring up that example to make a point: a plugged-up filter has risks beyond odors in your home. Let’s say it increases the static pressure of your furnace system, a common occurrence with clogged filters. That pressure will require the system to work harder to generate proper airflow in your home. In turn, you’re taking months or even years off the life of your system if this remains a neglected area.

So you might smell socks, but the bigger danger could be to your wallet as you’re forced into a system replacement years before the expected replacement date. And throughout that time, your heating and cooling will be operating less efficiently, providing you with far less comfort and far higher utility bills.

For emphasis, this can be a problem even during the winter months when you might not have the dirty sock smell.

That example is a worst-case scenario, but it also isn’t uncommon when an HVAC system isn’t properly maintained.

So are there risks to your health? Potentially. But it’s important to realize that your entire HVAC system is interconnected, and a problem that you notice with your nose isn’t necessarily limited to only that problem.

With that in mind, it’s important to fix this problem at the source, which can vary depending on your system and which areas are causing problems.

Short-Term Solutions

Sometimes a short-term solution is also a long-term solution. However, if your system developed Dirty Sock Syndrome once, what’s stopping it from developing again?

The items listed below may be necessary to clear out the odor prior to a long-term solution, but they should be paired, at minimum, with a visit from a licensed HVAC maintenance technician to inspect your system for other issues that may be causing the smell.


Change Your Filter

I talked about filters earlier because it’s a common area of neglect for HVAC systems. If a filter is dirty, it’s not functioning well. Or, worse, it’s clogged up and is functioning too well, to the point where it’s blocking airflow.

Filter changes can be a part of a maintenance package with your HVAC partner. It’s something that you as a homeowner can generally handle yourself, but baking this task into regularly-scheduled tune-ups and maintenance visits can remove the risk of forgetting to take care of it often enough.

Buy Your Filter

How often does your filter need to be changed? It depends on the filter type. Often, filters that catch finer particles will need to be changed out more frequently. In general, any filter will need to be replaced at least once per year, and it’s often as little as 60-90 days for some types.

Clean Your Evaporator Drain Pan

This is another item that can be handled professionally or by the homeowner. The only poor decision is to ignore it entirely. The drain pan can become plugged up or sometimes just starts collecting dirt that can lead to bacteria or mold. Ensuring that it’s clean is a good precautionary measure.

Have Your Ductwork Cleaned

Bacteria and mold can accumulate in your ductwork, particularly in joints and corners where there are small crevasses or where the airflow isn’t uniform.

This problem can be compounded by issues like poor filtration. If the airflow is blocked, or many particles are not being caught, problems will occur more frequently in your ductwork. A thorough cleaning is often a great way to remove many of the particles causing bad smells.

Have Your Evaporator Coil Cleaned

The hotbed for your Dirty Sock Syndrome is likely in the indoor evaporator coil that is part of the air conditioning unit. The coil absorbs moisture from the air, which is how it’s able to efficiently cool your home.

Cleaning an evaporator coil properly is a process that should be done by an HVAC technician. Any improper handling of the coil or other parts during the cleaning is on the homeowner if they attempt to do it themselves.

While a combination of these is almost certain to remove the odor, they don’t necessarily prevent the problem from happening again if the same conditions are in place within your home.

This is why you might also consider more long-term solutions.

Long-Term Solutions

These are the fixes that will work toward preventing the problem in the first place. They should be considered along with short-term solutions to form a holistic plan for your home.

Upgrade Your Filter

If replacing your filter is the short-term solution, considering an upgrade can often be an even better one.

Your options will depend on what types and sizes of filters your system can hold. Many can be upgraded from a one-inch air filter to a three-inch media filter that will catch a lot more, including a lot of bacteria and mold spores. This alone can sometimes prevent a problem from spreading throughout your system. However, if excessive moisture is the problem, you may have to look elsewhere.

RELATED: Aprilaire Media Filters

Invest in a Dehumidifier

Whole-home dehumidifiers have numerous benefits, including those to your utility bills and comfort. For our purposes, though, they can remove excess moisture in the basement that often leads to Dirty Sock Syndrome.

It’s true that air conditioners are designed to control moisture to an extent, so ensuring that your A/C unit is running efficiently is another good check. However, dehumidifiers can lighten the load on an air conditioner and trap excess moisture at the same time.

RELATED: Is a Whole-Home Dehumidifier Right For Me?

Utilize UV Technology

Ultraviolet light is very deadly to living things. This is pertinent for our purposes, because mold and bacteria wither in the presence of it.

Of course, your air conditioner is likely in your basement (or attic) and isn’t exposed to any kind of light. UV lights solve this problem.

At Fire & Ice, we carry and install the Reme Halo Air Purifier. Not only does it utilize this technology to kill bacteria in your system, but it also proactively releases particles into your home that bond with harmful viruses and bacteria, making them inert. As a ducted solution, it can provide this benefit for your whole home.

RELATED: The Reme Halo Air Purifier: Take Control of Your Home Air Quality

The Reme Halo is a powerful option to neutralize harmful particles, but it’s not the only UV light product out there. There are pros and cons to many of them, and each should be assessed before choosing one and having it installed.

Assessing Options

While items such as regularly changing your filter and checking your drain pan are good advice for any system, if you’re dealing with powerful, unwanted odors, it’s probably time to schedule a maintenance visit.

One or more of the solutions mentioned in this article might be the right fit for you, but it will depend on your home, your system, the particular concerns you have about your comfort and health, and your budget. Having a conversation with a licensed HVAC partner, while also ensuring that everything is clean and running smoothly, is the best first step to ensuring that you rid your home of Dirty Sock Syndrome and keep it away.

Ready to schedule your in-home service? If you’re in Columbus, OH, or the surrounding area, reach out to us today. You shouldn’t have to go another day with unwanted odors, and we’d love to discuss your options and help you make the best decision for your home.

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