Why Does My Air Conditioner Smell the First Time I Use it Each Summer?

April 15, 2016


This is an age-old question that many homeowners ask. Rest assured it is not uncommon for your air conditioner to smell the first time you fire it up for the summer season. In fact, it’s so common that it’s earned the name “Dirty Sock Syndrome.” So why does it happen and how can you prevent it?

Think about this, your air conditioner hasn’t been used for months; there can be dust and dirt left on it from last summer. That dust and dirt had time to collect and lead to mold and mildew, which is the source of the smell.

Where are this mold and mildew coming from? Mold and mildew can usually be found on these sources:

• Air conditioner filter
• Evaporator coil
• Ductwork

When is the last time you changed your air conditioner’s filter? The filter gathers dust and dirt from the air that can accelerate mildew growth when exposed to moisture. Last summer’s filter has been collecting odors for months. If you haven’t changed your system’s filter since last summer your whole home may be getting dirty air blown back into it.

The air conditioner’s filter may not be the only thing to blame for that foul odor. Another source of the problem could be the evaporator coil. The evaporator coils become both cool and damp, creating the perfect conditions for bacteria to grow.

If the air conditioner and the evaporator coil aren’t the culprits then the ductwork may be to blame. Poorly sealed ductwork or an ac system that is not removing moisture from the air as well as it should lead to mold and mildew growth. Duct cleaning can help improve your health and safety by eliminating bacteria and germs from the source and re-circulate air, leaving your home cleaner.

No matter the source of the smell, when air flows through the vents it spreads mold spores throughout your home.

To help conquer the mold and mildew smell have your evaporator coils cleaned, drainage lines should be inspected, the air filter should be changed, drain pans should be emptied (if applicable), and ductwork should be checked for possible leaks and mold/mildew growth.

Having your system regularly maintained will pay for itself in lower repair costs, less aggravation, more efficient operation, increased comfort, and also help to alleviate unwanted odors. Contact us for all of your air conditioning needs.


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Last Updated: June 09, 2023