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  • Writer's picture338 Aircon

Most Common Aircon Unit Smells And What They Mean

As a professional aircon servicing company, these are the questions we hear all the time from homeowners and business owners alike. When your aircon unit is starting to put out terrible odors, it’s never a good sign and it’s also definitely not good for your health.

Even worse than that, some smells are toxic and require urgent attention. One of the critical things that many home and business owners notice is bad aromas emanating from the air conditioning unit. An odor problem doesn’t necessarily mean that a repair will be expensive but definitely needs to be checked.

Here are the 6 most significant potentially toxic aircon unit smells that you may be smelling:

1) Burning or Electrical Odors

Electrical smells are a common air conditioning smell and could indicate a mechanical aircon issue with your aircon compressor or fan, electrical component failure, or a wiring issue.

These components are made from various chemicals and metals, and prolonged exposure to odors from these is not healthy. The first few times an aircon unit kicks on, it may emit a burning smell that can smell electrical or dusty.

Usually, after 20 to 30 minutes, the smell can dissipate. If it does, then it was probably burning off the dust in the unit. This is common after the unit has not been in use for a while. However, if it continues, you should contact a professional aircon servicing company to check out the problem and repair the unit.

Pro 338 Reminder: Electrical odors are typically an aircon issue with the aircon compressor, fan motors, or wiring. Attempting to fix these yourself can result in severe injuries. If you are not comfortable with trying repairs by yourself, then contact your local aircon unit specialist to look at it.

2) Gunpowder Smell

The gunpowder smell is the cousin of electrical odors. Distinctive gunpowder-like odors can be due to a fried fan motor or circuit board. Again with these made from various metals and chemicals, they can pose potential dangers to your respiratory system. Before starting up a system again after a prolonged dormant period, it should be inspected by an aircon professional.

3) Rotten Egg Smell

Provided you didn’t leave any rotten eggs hiding anywhere in your home; if you smell sulfur or it smells like rotten eggs emanating from your aircon unit, it’s most likely a natural gas leak. Although gas is odorless, utility providers add the aroma to alert people of a dangerous leak. So if you smell gas, there’s indeed an aircon issue.

Another reason for these types of aircon unit smells is you may have a pest problem or a dead animal somewhere in your ductwork or attic. So definitely best to get that checked out. If you do find something, call pest control to remove the dead animal.

Pro 338 Reminder: If it’s a gas smell, do not take it lightly. If you smell sulfur in your home, then natural gas is most likely the culprit, and immediate inspection of its source is required. You should turn off your gas supply immediately, evacuate your home, and call the fire department.

While low-level exposure in itself is hazardous to your health, high levels can reduce oxygen in your blood and lead to a loss of consciousness and even death. As we all know, gas is highly flammable and explosive and could result in fatalities as well. So if you notice this type of odor, open all of the windows in your home or business and get out of the building immediately. You should also contact your local natural gas provider.

4) Exhaust Fumes

Even if your aircon units are not powered by gas, exhaust fumes can be present if fluids leak from specific components in your aircon unit. To avoid such dangerous situations, If you smell exhaust-type fumes, you should contact your local professional aircon servicing company to assess your problem professionally.

Burning oil and other fluids can release large amounts of toxic gas into the environment. This gas can be different in its chemical makeup as it is in its original liquid form. These particulates can be very hazardous to your health when inhaled, depleting oxygen in your bloodstream, resulting in many serious health issues.

5) Chemical Aromas

Chemical smells can come from many different sources. The following may help you

decipher which one is the most likely culprit:

The aircon unit itself

If your aircon unit smells like paint thinner, formaldehyde, or any other chemicals, it needs to be assessed before use. Many fluids are used within your aircon system. They can be the culprit for an assortment of chemical-type smells when the unit malfunctions. Contact your professional aircon servicing company for a proper diagnosis.

Ozone Smells

Electrostatic-type air filters can produce ozone and emanate an odor that smells like chlorine. Also, certain types of UV lights installed to irradiate filter surfaces to kill bacteria can produce ozone. Ozone is very unhealthy for people if inhaled in large enough quantities. Some can experience chest pains, while others may have trouble breathing.

If you are unsure about what type of system you have. It’s best to call your professional aircon servicing company to check on your system.

Glue Odors

If you have recently had any ductwork done, this may answer your home’s chemical smells. The glue used for duct installation can give off a heavy chemical odor while it’s drying. In this case, the smell won’t go away immediately; you must wait for the smell to fade. Run your aircon unit fan, open the windows to your home or business, and wait for it to dissipate. If the problem persists, then discuss this with your local professional aircon servicing company.

Freon Leaks

Freon is a chlorofluorocarbon or CFC, which is also known as a refrigerant. Freon is used to remove heat from the atmosphere and transfer it to somewhere else, usually outside your home or business. This is what keeps you cool inside. It is also harmful when it’s not contained appropriately.

Freon travels within a closed system in condenser and evaporator coils and lines. Mostly made from copper, these coils and lines can sometimes crack and result in a refrigerant leak.

Pro 338 Tip: What does Freon smell like?

A freon leak smells like coolant in your car and has a slightly sweet aroma. Freon leaks can be toxic. If you suspect a refrigerant leak, then talk to your local professional aircon servicing company, who can use a freon leak detector to find and repair the issue.

6) Mold or Musty Smells

If you feel like your aircon unit smells like your grandma’s house then an aircon unit that smells like mold and mildew is one of the most common aircon smells coming from the aircon system. When the aircon unit is running, there is a lot of condensation that builds up within the unit.

If this moisture doesn’t drain properly, it can escape into the airflow and end up in the air ducts and cause mold buildup in your ductwork. This can be caused by a clogged condensate drain line. So it’s definitely worth checking out.

Mold is not a serious problem with the aircon unit itself. However, the poor indoor air quality that results from having mold in your system is dangerous to you and your family’s health.

Mold can increase the risk of respiratory infections in both children and adults. It is best to keep your aircon unit off until this problem can be remedied. So, if your aircon unit smells musty, it’s best to engage a professional to check it out.

Often the smells indicate that the system just needs a service. However, more serious odors like sulfur or gas indicate a much larger problem. If you are experiencing an electrical or burning odor, immediately shut down the unit and contact your local professional aircon technician. They can quickly diagnose any issue you have and recommend a variety of solutions to get your aircon back up and running safely.


It’s always a good time to talk about the common issues that aircon units have. This way, you’ll be able to spot if there are problems with your unit or not and prepare for its replacement accordingly. If you require our aircon servicing services, Whatsapp us at +65 9222 4141 for a fast and transparent quote.

338 Aircon Servicing Singapore provides an extensive range of Aircon Services including Aircon Servicing, Aircon Repairs, Aircon Installation of the best aircon brands, Chemical Overhaul, Gas Top-up, Aircon Leaking Water, and Aircon Not Cold Fix, and more. We have a team of professional technicians who are equipped with vast knowledge and experience in the Aircon industry.

We have over 15 years of experience in dealing with aircon works and have completed thousands of aircon works for both residential (Landed, Condo, and HDB) and commercial. We are a highly recommended Aircon Company in Singapore, with many delighted customers and reviews over the years on Google and Facebook.

WhatsApp us at +65 9222 4141 for a transparent quotation and honest pricing for all your aircon needs or Call us at +65 9222 4141 . We offer a fast and efficient service to serve any of your aircon needs!


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