A Smell Coming From My Portable Home Air Conditioner

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Portable air conditioners are convenient and, for the most part, trouble free. You can easily forget that these units do require some cleaning and maintenance to function efficiently. A dirty air conditioner can develop foul odours which can lead to inefficiency and potential health problems for you and your family.

Mold, Mildew and Odor

Most foul smells in a portable air conditioner are caused by mould and mildew growth. The unit's various components can become dirty and moist, providing the perfect environment for bacteria or fungus to thrive. Smells range from a mild musty odour often related to mildew to a rotten or spoiled food smell that indicates mould or bacteria growth. Without proper maintenance of the filters, coils and drains, a portable air conditioner can become overrun with mould but is easily cleaned away in most cases, and monthly cleaning or replacement of these parts prevents the odour from returning.


Dust and other small particles collect inside your air conditioner's filter, which prevents these things from entering other parts, such as the coils and drain line. When too much of this debris accumulates, an unpleasant odour can develop. Dirty filters also block airflow and reduce your air conditioner's efficiency. Filters are easily cleaned or replaced, depending on the model. If you have a reusable filter, remove the front cover from the unit, and take the filter out. Gently clean the filter with household detergent or vinegar and water to kill any mould and mildew and to clear the dust and dirt away. Rinse thoroughly and let the filter dry completely before putting it back in place. Clean or replace your air conditioner filter once each month to prevent odours from returning. If you use the air conditioner daily or have pets, you may need to clean it more frequently.

Drain Line

Dirty filters can result in mould and bacteria forming inside your air conditioner's drain, which can result in odours coming from your air conditioner. Remove the drain line, which is usually a plastic tube on the side of the unit facing outside, and flush with a mix of three parts water to one part bleach, which will kill mould or bacteria growing inside and clean away any debris that might be clogging the drain line. Allow the drain line to dry before replacing it. If your air conditioner also has a dripping pan, this should be pulled out and cleaned each month as well.

Evaporator Coil

Mold or bacteria growing in the evaporator coil can result in a bad-smelling air conditioner. The evaporator coils can usually be accessed by removing the top of the unit. Sprays are available from appliance parts stores for air conditioner coils that will kill mould and bacteria and prevent smells from developing. Before spraying the coils though, shine a flashlight inside and look for debris which can also cause mould and mildew growth. Remove anything large enough to pick out, such as leaves, and wipe the entire area with a wet cloth. If you see mildew or mould growth, use a mild household detergent to clean it away and rinse with water. Leave your air conditioner to dry completely before replacing the top and turning it on.

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