A bad smell can ruin the comfort of a cool and welcoming environment, and this unpleasant situation can occur when the air conditioner is turned on. There are various possible causes for this: let’s explore them to understand how to resolve the issue and avoid the annoying discomfort.

Why does my air conditioner smell?

If you notice a foul smell in the room after turning on the air conditioner, it is very likely that the device has an issue that needs to be addressed as soon as possible—not just to eliminate the odour itself, but also to protect the health of the home’s occupants. The microclimate and air quality can also be affected.

Several factors can cause the air conditioner to emit bad odours, ranging from the condition of the filters to the level of refrigerant gas inside. Let’s try to identify the types of bad smells depending on their various origins.

• If there’s a stench that resembles sewage, the problem is likely caused by an accumulation of condensation in the split unit, the central part of the air conditioner. This happens because the condensation isn’t properly drained through the discharge pipe. 
• If you notice a musty odour, it is likely due to dirty or clogged filters. The air passing through them isn’t being properly purified. 
• When the smell is mouldy, it indicates the development of mould and fungi inside the air conditioner, often due to excessive moisture in parts of the device, particularly in the condensation tray or filters. 
• A gas smell indicates a refrigerant leak. This requires immediate attention for both user safety and to ensure the air conditioner continues to function properly. 
• The smell of smoke or burning plastic could be caused by a malfunction in an electrical component such as circuits or wires.

Given the variety of potential causes, some of which are particularly serious, it is advisable to call a specialised technician for a thorough inspection and targeted intervention.

How to fix a smelly air conditioner?

Once the source of the problem is identified, it is possible to fix the issue, always keeping in mind that the best solution is to rely on the expertise of skilled technicians. Depending on the origin of the smell, different components will need to be addressed.

• Cleaning the filters can eliminate musty odours. After removing them from the split unit, dust should be cleared off, and they should be washed with water. The filters should be allowed to dry completely before being reinserted into the internal unit.
• An accumulation of condensation, which causes a sewage-like smell, requires cleaning the condensate collection tray and the drainage pipe.
• To remove mould, a thorough cleaning of the air conditioner is necessary, as mould can cause various health issues such as respiratory irritation, and prolonged exposure to spores can lead to sleep disturbances, nausea, and vomiting.

The first essential step is regular maintenance of both the internal and external units, with thorough cleaning and sanitization of the tray, as this is the most likely area for the accumulation and growth of bacteria, fungi, and mould.

What does air conditioner gas smell like?

If you notice a gas smell when the air conditioner is running, as mentioned earlier, it is likely due to a refrigerant gas leak inside the unit. However, it is not a strong or easily recognizable odour, as the gases commonly used in air conditioners are odourless.

That said, there are some clues that can indicate a refrigerant gas leak, including:

• the air produced by the indoor unit does not reach the set temperature;
• the formation of ice or condensation on the pipes of the outdoor unit.

In this case, the expertise of a skilled technician is essential to determine whether there is an actual gas leak or if the refrigerant level has simply decreased due to prolonged use of the device.

To recharge the air conditioner, the technician performing the inspection and maintenance must hold a specific certification, which qualifies them to handle fluorinated gases.

How to add fragrance to air from the air conditioner?

There are products on the market designed to scent the air coming from the air conditioner, offering a simple and immediate way to create a welcoming and pleasant environment.

For example, you can apply essences to the filters of the split unit, or use sanitising sprays designed to clean dust and dirt from the filters, which at the same time release a specific fragrance.

In both cases, the effect is temporary and fades over time, but it remains a viable option.

However, it is important that the use of essences and sprays is not intended to cover up bad odours coming from the air conditioner. This would only be a poor way to mask a problem that can be easily solved with the help of a skilled technician.