Nine Weird AC Smells and What They Mean

Air conditioning is an essential part of modern living, especially during humid summer months. When you run the air conditioner, you expect nice, cool, refreshing air to enter your home. But sometimes, AC units give off weird or concerning odors that make you curious if something’s wrong. 

A strange smell coming from your AC unit or ductwork might be no big deal — or it could signal a serious problem requiring immediate attention. When in doubt, turn off the unit and call an HVAC technician to check it out. In the meantime, learn about nine weird AC smells and what they might mean. 

1. Rotten Eggs 

A rotten egg smell could suggest a gas leak in your HVAC system. Air conditioners don’t function on natural gas, but they share a blower and ductwork with gas-fired furnaces, which could be the actual culprit for this smell. If you notice a rotten egg smell coming from the vents, turn off your air conditioner immediately, open the windows for ventilation and evacuate the house. Then, call an HVAC contractor promptly to check for a gas leak and perform the necessary repairs. 

2. Musty Odors 

A musty smell usually indicates mold or mildew growth inside the AC unit or ductwork. These microorganisms thrive in damp, dark conditions, making the evaporator coil and air filter common places for mold to set in. To get rid of the musty smell and prevent further mold growth, hire a specialist to clean your air conditioner, replace the filter and identify any other sources of moisture. 

3. Cigarette Smoke 

If someone in your home smokes, chances are the AC will start smelling like stale cigarettes before long. The compounding of nicotine and other chemicals inside the unit, air filter and ductwork circulates into your home every time the air conditioner runs. Change the filter regularly and schedule routine maintenance to help prevent this AC odor. Also, it would be wise to not smoke inside the house. 

4. Sewage 

If you perceive a sewage smell from your air conditioner, your plumbing or sewer system could have a problem. The smell may be caused by methane gas emitting from a busted or clogged sewer pipe or a dry drain trap, which has managed its way into the ductwork. Methane is dangerous, so if you smell a sewage-like AC odor, contact a plumber without delay. 

5. Stinky Feet 

A filthy air conditioner with a buildup of bacteria and fungi can emit a smell reminiscent of dirty socks. This odor may be notably strong when you turn on the AC for the first time in the spring. Regular cleaning and maintenance helps prevent this odor from developing. 

6. Skunk Smell 

If you smell a skunk-like odor coming from your AC unit, there may be a dead animal or animal waste inside the ductwork. There is the possibility that a sick or injured bird, rodent or other pest climbed inside an air duct during the winter, where it died and began decomposing. This is a health hazard, so get in touch with an HVAC technician to address the problem. 

7. Electrical Burning or Gun Powder 

If your AC emits a burning smell, it’s likely due to an electrical scenario, such as a damaged motor, circuit board, compressor or wiring. If any of these components overheat, they may emit a burnt, gun powder-like smell. To protect against permanent damage, turn off the AC immediately and call an HVAC technician to diagnose and fix the issue. 

8. Car Exhaust 

A smell similar to car exhaust could signify a refrigerant leak. Refrigerant is the chemical your air conditioner uses to remove heat from the indoor air and exhaust it outside. A leak can be a serious health and environmental hazard, so turn off your air conditioner and call for help. 

9. Chemical Fumes 

A chemical-like smell coming from your air vents could be traced to nearby vehicles, cleaning products, paints, adhesives or other toxins. If your AC blower fan motor is situated in the garage, even a car’s idling exhaust could mingle with the indoor air. These are serious concerns that could warrant sealing the ductwork or even redesigning your HVAC system. 

Schedule Air Conditioning Repair 

If you’re concerned about a weird smell arising from your air conditioner, turn to Robinson Service Experts for the repair you need. We use advanced diagnostic equipment to promptly and accurately determine the problem. Then, we’ll share the most cost-effective repair methods and offer recommendations to prevent a recurrence. We believe in our excellent work so much that we back every repair with a one-year 100% satisfaction guarantee! Contact a Service Experts office near you for more information or to request air conditioning repair in Waukegan.