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air conditioner smells bad

No one wants their home to smell bad. Bad smells can signal that something is wrong in your home, and it can be incredibly frustrating to try to identify the source of the smell. If you’ve noticed that your air conditioner smells bad, it can also be a sign that your unit isn’t functioning correctly. There are a few possible explanations for why this might happen, and fortunately, there are also some easy solutions.


Burning Rubber or Plastic

If your air conditioner smells like it’s burning, there’s something wrong with the wiring. Wiring problems are severe and should be fixed by a qualified technician as soon as possible. If you ignore a burning smell coming from your AC unit, it could lead to an electrical fire. 


Rotten Eggs 

Natural gas leaks generally cause a rotten egg smell from your air conditioner. Gas leaks are hazardous and should be fixed immediately by a professional. If you smell gas, turn off your AC unit and open all the windows to ventilate your home. Then, call your gas company to report the leak. 


Mouldy or Musty Smell 

A mouldy or musty smell from your AC unit usually means mould is growing somewhere in the system. Mould is harmful to your health and should be removed as soon as possible by a professional. In the meantime, you can try running your AC unit with the fan setting on “high” to circulate air through your home and help reduce the mouldy smell. 


Fishy Smell 

A fishy smell from your AC unit is usually caused by algae or bacteria growth in the water reservoir. This problem is common in window AC units that have been turned off for an extended period and then turned back on again. To fix this problem, you’ll need to clean the water reservoir with bleach and water according to the manufacturer’s instructions.


Dirty Socks

The phrase “Eau de sweat sock,” “dirty socks,” or “funky feet” are all used to describe a particular smell that arises from standing water or bacterial growth in your air conditioner. Despite being offensive, this air conditioning odour typically does no damage. If your air filter is blocked or moist, replace it. Next, get an HVAC expert to clean your air conditioner, paying specific attention to the drain and evaporator coil.


Garbage Smell

A rat, bird, or other animals that find their way into the ducts and perish often cause an unpleasant garbage-like odour. The AC system is transmitting the odour in your home. You’ll need to contact a professional to clean your duct system and eliminate the animal’s remains. Avoid using the air conditioner till then to reduce the spread.


Skunk Smell

It is most likely a skunk if the AC smells like one. If disturbed, skunks may spray the exterior condenser of your air conditioner. Your ducts will then be exposed to a strong odour. To stop the odour from spreading further, turn off the air conditioner. Ventilate your house by opening some windows. Call your neighbourhood HVAC technician to clean the condenser and the ductwork.


Cigarette Smoke

Cigarette smoke is one of the hardest smells to air out. If you’ve recently quit smoking or have smokers in your home, getting rid of the smell can be tricky. The first step is to clean all surfaces in your home, including carpets, furniture, and walls. You should also replace your air filter and use an air purifier to help remove the smoke particles from the air. If the smell persists, you may need to call a professional to clean your ductwork.


Sweet Smell

A sweet smell from your AC unit is usually due to antifreeze leakage. While this may not seem like a big deal, it can be hazardous—especially if you have young children or pets who might come into contact with the leaked antifreeze. If you notice this smell, shut off your AC unit immediately and call a professional for help.


Exhaust Fumes

If you smell exhaust fumes from your air conditioner, it could be due to a problem with the furnace. The furnace leaks carbon monoxide can cause serious health problems—even death. If you suspect your furnace is leaking carbon monoxide, evacuate your home immediately and call 911. Do not reenter your home until it has been checked by a professional.



If your air conditioner is giving off any bad smell, it’s essential to take action immediately. Some problems, like mould growth, can cause serious health problems. Other issues, like animal carcasses in the ductwork, can be tough to eliminate.


If you notice an unpleasant odour coming from your unit, don’t hesitate to contact a professional to help diagnose and resolve the problem!

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