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Preventing Molds From Growing On Your Aircon Unit

What exactly are molds?

Molds are microscopic fungi that live on plant or animal matter. Molds are a natural part of the environment and can be found almost anywhere that moisture and oxygen are present. Mold is not usually a problem indoors unless mold spores land on a wet or damp spot and begin growing. As molds grow they digest whatever they are growing on.

Are molds dangerous?

Yes, some molds are dangerous as some molds cause allergic reactions and respiratory problems. And a few molds, in the right conditions, produce “mycotoxins,” poisonous substances that can make you sick.

Why do molds grow on aircon units?

There are many types of molds, all of them need water or moisture to grow. When excessive moisture accumulates in buildings or on building materials, mold growth often occurs, particularly if the moisture problem remains undiscovered or unaddressed. Mold growth can occur on:

– Wood

– Paper

– Carpet

– Foods

– Insulation (Aircon Unit)

Health risks associated with indoor mold growth include:

– Sneezing

– Runny nose

– Red eyes

– Skin rashes

– Dizziness

– Headaches

– Asthma attacks

How detect molds on your aircon unit:

When mold is present in a large enough volume, it will begin to emit a distinctive smell. Many people describe the smell of mold as musty or earthy. The smell of mold may be unpleasant, but on the bright side, it makes larger mold infestations easier to detect.

When you have mold buildup in your aircon unit or aircon ducts, the smell will usually be strongest while your aircon unit is running. This is because the air that comes from your ducts will pick up and carry more mold spores as the mold inside the ducts spreads. When your system isn’t running, spores will settle inside the ducts and the smell will be harder to notice.

2) Symptoms of illness and allergy

By far the most significant risk of having mold in your aircon unit or air ducts is the health effects it can cause for your family. While breathing mold spores can cause symptoms in virtually anyone, some people have an allergy to mold spores that makes them especially sensitive to moldy ducts. Likewise, mold can exacerbate the symptoms of anyone in your family with pre-existing respiratory problems.

Allergy symptoms such as itchy, watery eyes, coughing and sneezing, and difficulty breathing can be signs of mold if they occur indoors, especially if they are more severe in rooms that are air-conditioned. In more serious cases, breathing mold spores can cause fatigue, nausea, vomiting and diarrhea, and confusion. A professional aircon servicing company recommends that you stop using your aircon unit until you’ve had it inspected for mold if you see these symptoms in your home.

Since the air from your aircon unit comes in contact with your vents first before it reaches the rooms in your home, it is not uncommon to see significant mold buildup on the vents. Spores will settle on your vents and appear as small spots that are usually black, green, or white in color. Even if you don’t see mold on the outside of your vents, you should remove them occasionally and check for mold growth on the duct-facing side.

Cleaning the mold off of your vents, done by a professional aircon servicing company will naturally make them look much better, and may reduce illness and allergy symptoms since mold is no longer growing directly in the room. To clean mold off of a vent register, remove it and submerge it in water, and then add laundry detergent and let it soak. This is a good time to vacuum out the exposed duct to remove as much additional mold as possible.

4) Mold inside the aircon unit

The same conditions that promote mold growth in your aircon ducts are also present inside your aircon unit. Mold can grow on virtually any surface as long as it is in a dark and damp environment. The mold in your ducts may have originated from mold growth in these appliances that were spread through your ductwork as you used your aircon unit.

The most common places to see mold growth in an aircon unit, are on the evaporator coils or in the drain pan beneath them. These components are frequently coated with condensation that can provide enough moisture for mold to flourish. You may see mold anywhere in your furnace as it heats and humidifies the air inside it.

How to prevent molds from growing in your aircon unit:

1) Keep an eye on humidity

Humidity is a natural cause of moisture which, in turn, is the main cause of mold. It is recommended that indoor humidity should only be in the range of 30% – 60% to discourage mold growth.

Some aircon units often share some properties with dehumidifiers, but if relative humidity exceeds 60%, you’ll likely find that the aircon unit might be ineffective in controlling humidity.

2) Don’t let your aircon unit be idle

Once your aircon unit is set up, it’s important to keep the unit running frequently to help prevent mold. One common mistake people make with their aircon unit is to let it idle or they let it sit in the window without actually running the unit for extended periods. You may think you’re being thrifty by keeping your electric bill down, letting that aircon unit idle but it completely shuts off the airflow running through the air conditioner, which can let that moisture build up and cause mold.

Instead, a professional aircon servicing company recommends running your aircon unit on a low setting while you’re away or even better, taking the time to clean out the aircon unit prior to leaving.

Those mold spores can also settle in dust inside your aircon unit. There are two places where dust is most likely to settle: on the filter or inside the unit itself.

To access the inside of the aircon unit, simply remove the front cover. This is a little different for each type of aircon unit, but generally, the front cover of the aircon unit will either be “spring-loaded” so you can remove it with your hands or latches you release with your hands. Worst case scenario, you may need to remove a few screws to get the front cover off. However, it is recommended that this should be done by a professional aircon servicing company as some parts of your aircon unit may be delicate and once touched improperly, may result in more serious aircon issues.

The filter for your aircon unit looks like a fine screen inside a plastic frame. It catches debris and air particles to prevent them from circulating into the room. The filter is a necessary part of the aircon unit, but the dust that accumulates on the filter can make it easy for mold to grow.

The filter is always found just behind the front grill and is typically reusable. To remove dust from the filter, simply run your hand-held vacuum or vacuum hose along with the filter, being careful not to damage the mesh screen. It may be reusable however, a professional aircon servicing company recommends that you replace the air filters once every 3 months or have them maintained regularly to properly achieve the right air quality from your aircon unit.

The best way to prevent any significant dust and moisture buildup throughout your aircon unit is to clean the unit once every few weeks. It is also recommended to have it done by a professional aircon servicing company and avoid DIY to thoroughly clean the inside parts of your aircon unit.

Pro 338 Trivia: Did you know that the first aircon unit was made to dry ink and keep paper straight in a printing press room? The aircon unit component was designed to wick away moisture, and in turn, prevent mold growth.


It’s always a good time to talk about the common issues that aircon units have. This way, you’ll be able to spot if there are problems with your unit or not and prepare for its replacement accordingly. If you require our aircon servicing services, Whatsapp us at +65 9222 4141 for a fast and transparent quote.

338 Aircon Servicing Singapore provides an extensive range of Aircon Services including Aircon Servicing, Aircon Repairs, Aircon Installation of the best aircon brands, Chemical Overhaul, Gas Top-up, Aircon Leaking Water, and Aircon Not Cold Fix, and more. We have a team of professional technicians who are equipped with vast knowledge and experience in the Aircon industry. 

We have over 15 years of experience in dealing with aircon works and have completed thousands of aircon works for both residential (Landed, Condo, and HDB) and commercial. We are a highly recommended Aircon Company in Singapore, with many delighted customers and reviews over the years on Google and Facebook.

WhatsApp us at +65 9222 4141 for a transparent quotation and honest pricing for all your aircon needs or Call us at +65 9222 4141. We offer a fast and efficient service to serve any of your aircon needs!  


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