Why does my air conditioner smell?

Fast read

An air conditioner should be improving the comfort of your home, but if you smell something strange coming from it, there may be an issue. Do not ignore it.  There are various possible smells your air conditioner could produce, and there could be a wide range of reasons behind them.

A gas-like smell indicates a gas/refrigerant leak within the system and requires immediate action to turn off the gas and call the supplier and installer. A burning or fire smell could be from an electrical part, such as a compressor, circuit board, or fans, or from a build-up of dust.

If the air conditioner smells like a car engine, there may be a leak in the refrigerant line, which carries a health risk. A mouldy smell is most likely due to the build-up of water and mould growth, or dirty filters. Make sure you have your air conditioning unit services every few years. 

Is your air conditioner producing a weird smell? 

Air conditioners should improve the comfortability of your home, not stinking the place out. If your air conditioner smells, it is likely unclean and even dangerous to your health, as for example it could be mould and spread mould spores. A qualified specialist should undertake routine maintenance on the air conditioner, and ensure it gets a thorough clean to remove whatever causes the smell.  

So what smell are you experiencing from your air conditioner?

Does your air conditioner smell like gas?

A gas-like smell coming from your air conditioner is not a good scenario. This smell could indicate that there is a gas leak within the system. Neutral gas does not smell, but manufacturers put a chemical called methyl mercaptan in the gas within an air conditioner so it has an odour. This allows the homeowner to realise there is an issue. If this gas leak occurs, the gas will get into the ductwork and spread through the house.

If you detect this smell, turn your aircon off ASAP. Then contact your air conditioner installer to investigate and repair the issue.

Does your air conditioner smell like it is burning?

Within an air conditioning unit, there are various electrical parts. If you notice a fire or burning smell coming from your unit, the issue probably stems from one of these electrical parts. The compressor, circuit board, fans, or another component could be smouldering. Do not take your unit apart and try to resolve the issue yourself. Instead, turn off your system and contact your installer. 

Another cause of a burning or fiery smell coming from your air conditioner is a build-up of dust. Dust can get inside the unit if you do not clean your air conditioner. If you do not use your system for a while and turn it on, this dust can when heated evaporate and cause a burning type small. The fire risk is minimal, but if you get a burning smell, contact your professional to ensure no other unit components are affected.

While an air conditioner on fire is a rare occasion, make sure you prevent dust build-up in the outdoor unit, which after prolonged dry weather could present a combustion risk

air con on fire

Does your air conditioner smell like your car’s exhaust?

If your unit smells like a car engine, there is probably a leak in the refrigerant line. The refrigerant is the cooling agent in the air conditioner, and a leak impairs the unit’s performance. The leakage can also cause chemicals to be released into the air, which puts health risks in your home. 

So, if you notice this smell, turn the air conditioner off and open your windows. This will help try and filter the air out in case it is carrying a dangerous chemical. If you have a different air filtering device, turn that on. Contact an air conditioner professional to come out and assess the problem.

Does your air conditioner smell mouldy?

A mouldy smell from your air conditioner is the most common smell. The usual cause of this scent is the build-up of water in the drip lines or drip pan. The water can cause mould and fungus to grow. Another potential cause of this smell is having dirty filters. If your air conditioner is in a humid environment for a prolonged period, moisture can accumulate in the filters.

If you start smelling a mouldy or musty odour, it could be mould or mildew growth within the unit. As the air conditioner uses moisture in the air for cooling, there are a few points at which moisture can build up if the air conditioner is not maintained correctly.

Mould and mildew can then grow and be blown out of the aircon unit into the house. This can be a risk to the occupants of the house due to the bacteria associated with the mould, which can negatively affect your health. In this case, getting a trained technician to service and clean your air conditioner to remove the mould and service the unit to prevent this from reoccurring is essential. 

dirty air conditioner filter
Regular cleaning of your air conditioner’s filters will prevent mould growth, spreading spores and smells from being created

Dust and dirt accumulation

Dust particles and other small items can block up filters over time, creating a stale or musty smell. You can easily remove the filters from the air conditioning internal unit and clean them with a hose and soapy water yourself. Make sure you use a steady ladder and have another person nearby when you work up high. We recommend further cleaning around vents or ducts to maximise airflow.

Rodents and Pests

If you have issues with rodents and pests within your roof cavity, it could be possible that either they are dropping their waste in an area where the odours are being picked up and circulated by the air-conditioner or that something has died in the cavities or ducts for the air conditioning. This will be a very unpleasant smell and hard to ignore. Again – call a professional. 

In summary

If you are experiencing a bad smell from your air conditioner, it is vital to address the issue as soon as possible to prevent further damage to the unit and to improve the air quality in your home. Do not ignore it. When the problem persists, or you are unsure how to fix it, you should contact a professional HVAC technician for assistance.

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