Why Does My Air Conditioner Smell?

May 24, 2021

When there’s a persistent bad smell coming from your air conditioning system, it’s a serious indoor comfort problem. Ignoring the problem isn’t a possibility because dirt buildup or a dead animal in the ducts could be causing the bad smell. In some situations, it’s even dangerous to continue running your AC. Watch out for these common stinky culprits.


Air conditioning systems need to be cleaned once a year to prevent problems like bad smells, excessive energy use and inadequate cooling. To have your AC cleaned, hire an AC company for maintenance. Dirt builds up on the AC’s coils and other components over time. It’s one of the most common reasons behind a stinky air conditioner.

Mold and Mildew

Mold and mildew are also common reasons behind an AC that smells bad. They may mix with the dirt buildup as well. You can reduce the chance of mold and mildew growing inside your AC by scheduling cooling maintenance once a year. These biological contaminants can grow on your system’s coils, drain pan, and filter. They could also be growing in the air ducts. If you have your ducts cleaned every three to five years, you reduce the chances of mold and mildew growing inside of them.

Gas Leak

A rotten egg or skunk-like smell could mean there’s a gas leak. You should turn off the AC and the gas supply and call a repair company. Also, leave the house until it’s safe to go back inside. Ask your gas company to turn on the gas supply once you return home to ensure it’s safely turned back on.

Another possible reason behind a rotten egg smell is a dead animal. You have no way of knowing what the cause is, so always take the possibility of a gas leak seriously. Only an AC technician can let you know what the source of the smell is.

Dead Animal in the Ducts

Sometimes, an animal dies inside the ducts, which causes a bad odor to circulate throughout your home when the AC runs. You can have an AC company check your ducts for dead animals when the technicians come over to troubleshoot the reason behind the bad smell.

Sitting Water

When an area of your air conditioning system is clogged, it can result in sitting water from improper drainage. The sitting water creates a bad smell over time. If your AC smells like feet or sweaty socks, then this may be the cause behind the odor. Air conditioning technicians can solve this problem by thoroughly cleaning the system.


Fluids from the engine or other parts of the air conditioner may leak, which can cause an exhaust fume smell. You need to immediately have an AC leak fixed to prevent additional damage to your system and home. Chemical leaks can be hazardous to the environment and your family. While waiting on the repair technicians, you can open windows to improve ventilation, or you can temporarily leave. You don’t want to breathe in a lot of fumes.

Shorted Fan Motor or Circuit Board

The smell of gunpowder might circulate throughout your home when the fan motor or circuit board shorts out. Only certified air conditioner repair technicians can fix this problem. Another possible reason behind a gunpowder smell is an electrical component that’s burning. You need to turn off the AC because if any electrical component is burning, it’s dangerous. Don’t attempt to fix it yourself either because you could seriously injure yourself. Burning electrical components may also give off a burning plastic smell.

Burning Smell

A regular burning smell often means that dust is burning. If you have just turned on your air conditioner for the warm season, then this, most likely, is not a concern. The smell should go away within a day. If the burning smell persists, however, you will need air conditioning technicians to examine your system. A very strong smell is also a cause for concern. You should turn off the system if it malfunctions in any other way. Such a breakdown likely indicates that your air conditioner is broken. Air conditioning problems include blowing warm air, weak airflow, and short cycling.

Home Heating Service, Inc. provides air conditioning repair, maintenance, and installation services in Colorado Springs. Our company has been in business since 1988 and has won numerous awards, including the Angie’s List Super Service award. Other services we offer are heating services, cooling services, duct cleaning, duct sealing, indoor air quality, water heater services, and home upgrades.