3 Common Bad Air Conditioner Smells: How to Get Rid Of Them?

Your air conditioner is an essential appliance in your home. It keeps you and your loved ones cool and comfortable during humid days. Besides maintaining the right temperature and moisture level, it also improves air quality throughout your living space. 

Despite its ability to create a healthier, clean environment, your air conditioner can eventually deteriorate over time. For instance, a horrible stench can fill the room every time you turn it on. To learn more about how to address this issue, here are common bad smells from air conditioning units and what to do to get rid of them:

Musty Mildew

A musty or mouldy stench from the air conditioner is the most common smell encountered by many homeowners. This is caused by the accumulation of water in the drip lines or drain pans that result in fungus or mildew growth. One obvious sign to watch out for in your indoor ductless unit is water dripping down the wall.

Another reason for a musty smell is dirty filters. Moisture can eventually accumulate in the filters if your air conditioner stays on for too long. This is common among households facing a humid climate. To get rid of the smell, check the filters for blockage or moisture. Then, seek air conditioning repair to get the lines and ducts thoroughly cleaned. 

Rotten Eggs

A rotten air conditioner smell is usually caused by dead rodents or critters being stuck in the unit. Insects and birds can also nest and make the ductwork their home. Eventually, they can get trapped in the appliance with no way out. Over time, these dying or stuck animals can damage different components within the system and discharge a foul smell into your home. This can easily be prevented by making your unit pest-proof with help from a skilled technician.

Besides animal carcasses, a gas leak getting into the ductwork can cause a similar stench in your unit. This is because rotten eggs and sulphur almost smell the same. Note that natural gas is a hazardous substance that can catch fire and explode. Because of this, as soon as you smell a rotten air conditioner stench, turn off the gas supply right away, instruct everyone to leave the house, and report the leak. 

Cigarette Smoke

If you smoke indoors, the evaporator coil and filter absorbs the bad odour. Your air conditioner will eventually end up smelling like cigarette smoke every time you turn the unit on because the embedded tobacco particles are knocked loose and sent back throughout the room through the vents. 

Unfortunately, this unpleasant smell can cause headaches, nausea, and allergic reactions. To eliminate this smell from the vents, make it a habit of changing or cleaning the filter every 30 days and seek HVAC maintenance to have it professionally cleaned at least once a year. Consider also smoking outdoors.


A bad air conditioner smell may only seem like a minor inconvenience, but it is not good for your health. Instead of delaying proper repair work or trying to do DIY repairs, leave the job to professionals like us. We are equipped with the necessary tools, experience, and knowledge to finally eliminate the stench in your room.

At Legacy Heating and Cooling, we install and repair air conditioning in Edmonton and nearby areas. We also offer comprehensive HVAC products and services at cost-effective rates. Request a quote today!

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