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Does your air conditioner smell? Here’s what it means

First time using your air conditioner? Find out what odors are normal and when to get expert help.

A musty smell from your air conditioner is normal the first few times you use it each season. However, you shouldn’t ignore it. Some odors are common and some may be a symptom of a more serious problem.

Young man smells something bad and holds his nose
Shutterstock: Andrey_Popov

Dirty sock syndrome (yes this is a thing)

WHAT IT IS: Dirty sock syndrome is that moldy odor you get when you turn on your air conditioner for the first time of the season. As the name suggests, the smell is musty – not unlike a gym locker room – which is how we got the name Dirty Sock Syndrome. After a long period of time without use, mold and bacteria can build up on your evaporator coil or other areas of your HVAC system.

WHAT TO DO: If the smell lingers after repeated use we recommend having your evaporator coil cleaned by a professional. Especially for asthma and allergy sufferers, the mold spores and bacteria that is circulated in the air can cause problems. Other steps you can take include:

  • Check your filters
  • Clean the drain pan
  • Check your ductwork

IS IT DANGEROUS?: Generally no. It’s also possible that the smell is not related to mold – and even if it is, most molds are not dangerous in most cases. It is however annoying and embarrassing and not something you want to let linger throughout the cooling season.


Electrical burning smell

WHAT IT IS: :A burning electrical smell could mean you have a problem with the fan or compressor motor.

WHAT TO DO: Get help. An electrical burning smell could be a sign of a serious problem.

Schedule seasonal maintenance

The best way to get the most out of your air conditioner (and avoid unwanted odors and issues) is to have a Trane Comfort Specialist™ inspect and service your heating and cooling system regularly. We recommended:

  • Air Conditioner – Service once a year. Schedule in spring before hot weather arrives.
  • Furnace or heat pump – Service once a year. Schedule in the late summer or fall before cold weather arrives.

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