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Nine Suspicious AC Smells and What They Mean

Air conditioning is an essential part of modern indoor comfort, especially during the hot summer months. When you run the air conditioner, you want wonderful, cool, refreshing air to flow into your home. But occasionally, AC units produce strange or concerning odors that make you curious if something’s wrong.

A strange smell emitting from your air conditioner or ductwork might be nothing to worry about — or it could suggest a critical problem necessitating prompt attention. When you have a question, turn off the unit and call an HVAC technician to look a little more closely. Right now, read about nine weird AC smells and what they might mean.

1. Rotten Eggs

A rotten egg smell could point to a gas leak in your HVAC system. Air conditioners don’t function on natural gas, but they utilize the same ductwork and blower that your furnace uses, which could be the actual root cause for this smell. If you notice a rotten egg smell originating from the vents, turn off your air conditioner right away, open the windows for ventilation and evacuate the house. Then, call an HVAC contractor right away to inspect for a gas leak and execute the necessary repairs.

2. Musty Odors

A musty smell usually denotes mold or mildew growing inside the AC unit or ductwork. These microorganisms thrive in damp, dark conditions, making the evaporator coil and air filter likely places for mold to develop. To remove the musty smell and prevent further mold growth, hire an expert to clean your air conditioner, replace the filter and identify any other sources of moisture.

3. Tobacco Smoke

If an individual in your home smokes, most likely the AC will start smelling like a smokey dive bar eventually. The buildup of nicotine and other chemicals inside the unit, air filter and ductwork spreads into your home every time the air conditioner runs. Change the filter arrange for routine maintenance to help counter this AC odor. Also, it would be wise to not smoke inside the house.

4. Sewage 

If you notice a sewage smell from your AC unit, your plumbing or sewer system may actually be the problem. The smell may be caused by methane gas emitting from a damaged or blocked sewer pipe or a dry drain trap, which has found its way into the ductwork. Methane is hazardous, so if you smell a sewage-like AC stench, contact a plumber without delay.

5. Stinky Feet 

A nasty air conditioner with a buildup of bacteria and fungi can emit a smell reminiscent of dirty socks. This odor may be particularly strong when you switch on the AC for the first time in several months. Regular cleaning and maintenance helps to prevent this odor from happening.

6. Skunk Smell

If you smell a skunk-like odor coming from your AC unit, there may be a decayed 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 reach out to an HVAC technician to address the problem.

7. Electrical Burning or Gun Powder

If your AC produces a burning smell, it’s probably due to an electrical concern, 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 prevent permanent damage, turn off the AC now and contact an HVAC technician to diagnose and correct the issue.

8. Car Exhaust

A smell identical to car exhaust could indicate 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 major health and environmental hazard, so turn off your cooling system and call for help.

9. Chemical Fumes

A chemical-like smell emerging from your air vents could be attributed to nearby vehicles, cleaning products, paints, adhesives or other toxins. If your AC blower fan motor is positioned in the garage, even your vehicle’s idling exhaust could seep into the indoor air. These are serious concerns that could call for sealing the ductwork or even reworking your HVAC system.

Schedule Air Conditioning Repair

If you’re thinking about a weird smell originating from your air conditioner, consider Service Experts Heating, Air Conditioning & Plumbing for the repair you need. We use advanced diagnostic equipment to quickly and accurately define the problem. Then, we’ll summarize the most cost-effective repair methods and offer recommendations to prevent a recurrence. We believe in our exceptional work so much that we back every repair with a one-year 100% satisfaction guarantee! Call a Service Experts office near you for additional details or to request air conditioning repair in the U.S..

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