Air conditioners are typically odorless, which is why it is alarming when your air conditioner smells bad. A bad smell coming from your air conditioning system is indicative of a number of problems from mold growth to frizzed wiring.

In this article, we explore the most common air conditioner smells, as well as what they mean. It is important to be aware of the smells coming from your air conditioner as some, such as a skunk’s smell and a chemical smell, indicate hazardous chemical leaks from your air conditioner.

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8 Common Air Conditioner Smells and How to Prevent Them

#1 Musty Smell means Mold and Mildew

A musty smell definitely indicates mold and mildew growth. Mold and mildew give off musty odors that smell damp and decayed. Check your air filter, evaporator coil, and air ducts for possible mold growth as these are the areas where mold is most likely to thrive in.

Mold and mildew often form when the air conditioner freezes up and melts, providing sufficient moisture for spores to thrive. Clean your air conditioner frequently, and allow the unit to dry completely before using again.

#2 Burning Smell means Burnt Wires or Electrical Faults

If your air conditioner smells like it's burning, it most probably is! Immediately turn your AC unit off, and unplug the unit to prevent electrical fires. That burnt odor means wiring within your unit is on the fritz, and has the potential to start an electrical fire. Contact your fire department if the burnt smell is accompanied by smoke.

#3 Skunk Smell means Gas Leak

That foul, skunk-like odor indicates a leak - and the smell is added into gas for a reason. Natural gas is relatively odorless, which is why a chemical compound called mercaptan is added into gas to alert people of possible gas leaks. This compound is what gives off that skunk smell.

It is best to shut your air conditioner off, turn off the main gas supply, and call your gas company to find and fix any gas leak inside your home. Avoid using or plugging electrical devices during this time, and air out your home by opening windows.

#4 Dirty Sock Smell means Stagnant Water

A dirty socks smell, also known as the Dirty Sock Syndrome, is a common occurrence in the drain pan of air conditioners. As the drain pan fills up with condensate, bacteria and fungus can grow in the stagnant water and give off that clammy foot odor. Clear the drain pan frequently, as well as the condensate drain line where bacteria may thrive in moist conditions.

#5 Car Exhaust Smell means Refrigerant Leak

While your air conditioner does not run on gas to cause exhaust fumes, a refrigerant leak can cause coolant to burn, which emits an exhaust-like odor through your air conditioner. Turn the air conditioner off immediately, and contact the best aircon service in Singapore to diagnose and solve the problem for you.

#6 Rotten Egg Smell means a Dead Animal

But it can also mean a gas leak. The strong odor from rotten eggs comes from sulphuric acid, which also occurs when organic material decomposes. If there is a strong smell of death coming from your air conditioner, chances are an animal made its way into your air conditioning vents and died. This is one of the common central air conditioner smells.

Alternatively, a natural gas leak may sometimes smell like rotten eggs, and can occur near your aircon ductwork. The best course of action in this case is to turn the air conditioner off, then look for the root cause of the problem within the vents and in the AC unit itself. Call your gas company immediately if you suspect a leak, and shut off the gas supply when possible.

#7 Cigarette Smoke Smell means A Smoker in the House

If your air conditioner smells like cigarette smoke both when you use the appliance and when it is shut off, then most likely the aircon filters took on the smell of cigarette smoke from someone smoking indoors. You can prevent this by smoking by an open window instead, and cleaning your air conditioner frequently to remove the stuck-on odor.

#8 Ammonia Smell means Mycotoxins

A strong ammonia-like smell indicates mycotoxins, which are released by large mold colonies. Some people describe the odor as the smell of a litter box or urine. The chemical smell may also indicate a coolant leak, which may smell like ammonia, paint thinner, or other strong chemical. Turn your AC unit off, then contact an aircon service company in Singapore to diagnose the problem.

Our Final Words

A smelly air conditioner does not just irritate your nose, it can lead to poor indoor air quality and health problems. Not to mention, a burning odor is highly dangerous as electrical fires can result from frizzed wiring. Air conditioners often get problems due to poor maintenance and infrequent cleaning, which causes the air conditioning unit to break down over time.

Tackle aircon maintenance before problems occur through one of our aircon servicing technicians! Go for a general cleaning, where we clean the interior and exterior of your unit to prevent mold growth, a chemical wash to keep all aircon parts in good working condition, or aircon maintenance that fixes small issues before they become big problems.‍