Why your air conditioner smells bad and how to fix it

When the weather calls for air conditioning, there’s nothing worse than turning it on only for your home to fill with a bad smell. A bad air conditioner smell is actually very common, but fortunately, pinpointing the cause and the solution is usually quite simple.

In this article, we look at some of the most common reasons why your air conditioner smells bad, along with some easy fixes that should solve the issue with minimal effort.

Table of Contents

Why does my air conditioner smell like mould or mildew?

A photo of a women and man sitting on a sofa, looking back at an air conditioner

The drain pan is full

The drain pan in an air conditioning unit is there to collect water that collects via condensation during the cooling process. If the pan fills or becomes blocked, it’s possible for mould to grow. The smell of the mould may then be spread around your home when the air conditioner is turned on.

Evaporator coil issues

Evaporator coils remove heat from the air, so they are a vital part of any air conditioning unit. However, over time mould can accumulate on and around evaporator coils, resulting in a mouldy smell coming from your air conditioner.

Excess moisture in ducts or vents

Mould and mildew love moisture, so when there’s excess moisture in the ducts and vents in your air conditioning system, it’s creating the perfect environment for mould to grow. When air is blown through the vents or ducts, the musty smell will spread through your home.

What to do

Empty and clean the drain pan

If you have a mouldy smell coming from your air conditioner, the first thing to do is check your drain pan. If it’s full, empty the water out, and it’s also advisable to give it a quick clean with soap and water to remove any possible build-up of mould inside.

Clean the air conditioner filters

Your air conditioner’s filters naturally catch dirt, dust, and debris from the air. If they become blocked, mould can grow in the vents and ducts around them. Cleaning or replacing your air conditioner filters can often solve the issue.

A photo of a person switching the filters on an air conditioner

Call a professional

If you’re bothered by the mould smell coming from your air conditioner and can’t find the source, it may be time to call a professional.

Use nanoe™ X with your air conditioner system

Panasonic air conditioners equipped with an internal cleaning function with nanoe™ X Generator Mark 3 can inhibit the growth of mould inside the air conditioner that causes the moldy smell.*¹

> Learn more about nanoe™ X Generator Mark 3

Why does my air conditioner smell like gas or rotten eggs?

A photo of man holding his nose

Leaking gas

A smell of rotten eggs or sulphur coming from your air conditioner is likely to be caused by leaking gas that’s getting into your air conditioner. This can be serious, so you shouldn’t ignore the signs.

Dead animal

Occasionally, animals such as rodents or birds can make their way into air vents and air conditioning systems. If the animals die, they can give off an unpleasant “rotten egg” smell as they decompose, which is then circulated through your house by the air conditioner.

What to do

Shut off your gas and call your gas company

If you suspect a gas leak, immediately shut off your gas supply and call your gas provider.
They will give you advice and, if necessary, send a technician to source and fix the leak.

Remove the animal and/or call pest control

If possible, check any accessible vents and ducts for signs of a dead animal. If you can’t find it but suspect there is one out of reach, the simplest fix is to call a pest control professional.

Why does my air conditioner smell like socks or dirty feet?

Dirty drain pan or evaporator coil

If your air conditioner is giving off a smell that reminds you of dirty socks or feet, a dirty drain pan or evaporator coil could be responsible. If they aren’t cleaned for a long time or get blocked, either part can attract microbial growth that can give off unpleasant odours.

Dirty air filters

When air filters become clogged by dust and dirt, microbes can grow in the air conditioner leading to bad smells that can spread through your home.

What to do

Clean the evaporator coil and drain pan

To solve the issue, the first thing you can try is cleaning the drain pan and evaporator coil.
This should remove the source of the smell.

Clean the air filters

Cleaning or replacing dirty filters should help to reduce the dirty-sock smell coming from your air conditioner by limiting microbial growth.

Why does my air conditioner smell like burning?

Components in the air conditioner are overheating or burning

As you might suspect, a burning smell coming from your air conditioner can be a sign that components in the air conditioning system are overheating or even burning. Needless to say, this is a potentially dangerous issue that should be taken seriously.

The air conditioner is being used after a long period of inactivity

If you’re getting a burning smell from your air conditioner after not using the unit for a long time, it may simply be a temporary smell caused by components moving and heating up after inactivity. If it goes away quickly, then it’s likely not a serious issue.

What to do

Call a professional

If the burning smell is persistent, you should turn off your air conditioner and call a professional to diagnose the issue.

A photo of a person opening an air conditioner

Why does my air conditioner smell like cigarettes?

Cigarette smoke getting into the air conditioning system

If you smell cigarettes when using your air conditioner, it’s almost certainly a result of somebody smoking in the vicinity of your air conditioning unit or vents. If anybody in your household smokes indoors, then cigarette smoke and smoke residue can build up in the air conditioning system and be dispersed when it’s turned on. It’s also possible that somebody smoking outside near a vent could be directing smoke into your home’s ventilation system.

What to do

Avoid smoking around the air conditioner

The simplest fix is to avoid smoking cigarettes in your home or around the air conditioning system.

Use nanoe™ X

Panasonic air conditioners installed with nanoe™ X technology generates highly reactive hydroxyl radicals into the air. These bind to the substances that cause cigarette smoke to smell and deodorise the odour in the room. This deodorised odour will help accumulate less cigarette smell on to the air conditioner itself.

How to prevent your air conditioner from producing bad odours

Prevention is always better than cure, and simply staying on top of basic air conditioner maintenance can go a long way toward preventing bad smells.

Keep your air conditioner clean

Try to clean your AC unit regularly. Some of the most important areas to focus on are the drain pan and around vents.

Change your air conditioner’s filters regularly

Air conditioner filters get clogged up over time, so keep an eye on them and change them in line with the manufacturer’s recommendations.

Use nanoe™ X

Panasonic air conditioners equipped with the internal cleaning function of nanoe™ X are a simple way to reduce bad odours and prevent them from developing. With Panasonic air conditioners equipped with an internal cleaning function with nanoe™ X Generator Mark 3 can also inhibit the growth of airbone and attached mold bacteria as well. By inhibiting microbial growth of bacteria, viruses, and both adhered and airborne moulds within your air conditioning unit, nanoe™ X can tackle bad smells at the source.*¹

nanoe™ X also inhibits allergens, pollens, pesticide residues, and PM2.5 pollutants, keeping the air in your home clean and fresh.

*1 While this function is effective in inhibiting mould growth, it does not prevent mould from occurring. The mould growth inhibition effect may vary depending on the installation environment and operating time. *When using the nanoe™ X Generator Mark 3 function, a multi-function wired remote control (CZ-10RT4C) is required. (The floor-standing type with a built-in control switch in the main unit can be used.) *Only ON/OFF operation is possible with the multilingual wired remote controller (CZ-10RTF4). Also, local setup is required to use the nanoe™ X Generator Mark 3.

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