Mould in Aircon is More Common Than You Think: How to Fix It and Prevent It

If you’ve ever noticed a musty smell when turning on your air conditioner, mould could be the culprit. Mould in air conditioning units is far more common than most people realise, thriving in the cool, damp environment inside your system.

Because aircons circulate air throughout your home, they can easily spread mould spores, affecting indoor air quality and even causing health issues like allergies, respiratory problems and headaches.

The worst part? Many people don’t even realise they have mould in their aircon until it becomes a serious problem. Regular cleaning and maintenance are key to preventing mould growth and keeping your home’s air fresh and healthy.

In this blog, we’ll cover why mould forms in air conditioners, the risks it poses, and − most importantly − what you can do to stop it.

Why Mould Grows in Air Conditioners

Mould loves damp, dark and humid spaces − exactly the kind of environment an air conditioner provides. When warm air passes through your AC unit, it cools down, leading to condensation.

This moisture, combined with dust and other organic particles, creates the perfect breeding ground for mould and bacteria.

One of the biggest culprits is poor ventilation. If your aircon isn’t getting enough airflow or if the filters are clogged, excess moisture can build up inside. Similarly, if your unit isn’t draining properly, stagnant water can encourage mould growth.

Another common issue is infrequent cleaning. Over time, dust and debris collect inside your aircon, giving mould the fuel it needs to thrive. That’s why regular maintenance, including cleaning filters and checking drainage, is essential to keep your system mould-free.

Signs Your Air Conditioner Has Mould

Mould in your air conditioner isn’t always easy to spot, but there are some clear warning signs to watch out for. If you notice any of the following, mould could be growing inside your unit:

• Musty or damp odour – A strong, musty smell when your aircon is running is a telltale sign of mould. The odour may linger even when the unit is off.
• Visible mould growth – Black, green or white spots around the vents, on the filters, or inside the unit indicate a mould problem.
• Increased allergy symptoms – If you or your family members experience sneezing, itchy eyes, coughing or respiratory issues while indoors, mould spores could be circulating in the air.
• Frequent headaches or fatigue – Prolonged exposure to mould can cause headaches, dizziness or fatigue, especially in enclosed spaces.
• Excess moisture or water leaks – If your air conditioner has drainage issues or condensation buildup, it creates the perfect environment for mould to thrive.

If you notice these signs, cleaning your unit or calling a professional can help prevent further issues.

Health Risks of Mould in Your Aircon

Mould in your air conditioner isn’t just an unpleasant sight or smell − it can seriously impact your health. As your aircon circulates air, it can also spread tiny mould spores throughout your home.

Breathing in these spores can trigger allergies, asthma and other respiratory issues, especially for children, the elderly and those with weakened immune systems.

Common symptoms of mould exposure include sneezing, coughing, itchy eyes and skin irritation. In more severe cases, mould spores can lead to persistent sinus infections, headaches and even difficulty breathing. Long-term exposure has been linked to more serious respiratory conditions.

If you notice a musty odour or experience unexplained allergy-like symptoms when your AC is running, mould could be the culprit. Regular cleaning and maintenance are crucial to preventing mould from growing in your unit and protecting your indoor air quality.

If you suspect a serious mould problem, it’s best to call in a professional to safely remove it and ensure your aircon is circulating clean, healthy air.

How to Remove Mould from Your Air Conditioner

If you’ve discovered mould in your air conditioner, it’s important to clean it properly to prevent it from spreading. Here’s how to safely remove mould from your unit:

• Gather your cleaning supplies
  • Rubber gloves, a face mask and protective eyewear
  • White vinegar or hydrogen peroxide (avoid bleach, as it can damage AC components)
  • A soft brush or sponge
  • A spray bottle and clean cloth
• Turn off and inspect your aircon
  • Switch off the unit and unplug it for safety.
  • Remove the front cover and check for mould on the filters, vents, and coils.
• Clean the affected areas
  • Spray a vinegar or hydrogen peroxide solution onto the mouldy areas.
  • Let it sit for 10-15 minutes, then gently scrub with a brush.
  • Wipe down all surfaces with a clean cloth.
• Replace or clean the filters
  • Wash reusable filters with soapy water and let them dry completely.
  • Replace disposable filters if they show mould growth.

If mould keeps coming back, it’s best to call a professional for deep cleaning and maintenance.

How to Prevent Mould Growth in Your Air Conditioner

Stopping mould before it starts is the best way to keep your air conditioner clean and your indoor air fresh. Here’s how you can prevent mould from growing in your unit:

• Clean or replace filters regularly – Dirty filters trap dust and moisture, creating the perfect environment for mould. Clean reusable filters every two weeks and replace disposable ones as needed.
• Keep your AC dry – Moisture buildup is a major cause of mould. Ensure your aircon’s drainage system is working properly and empty any water collection trays.
• Improve ventilation – Good airflow helps prevent excess humidity. Use ceiling fans or open windows occasionally to keep the air moving.
• Use a dehumidifier – If you live in a humid climate, a dehumidifier can help reduce moisture in the air, making it harder for mould to grow.
• Schedule regular maintenance – Have a professional check your aircon at least once a year to clean internal components and ensure everything is working efficiently.

By following these steps, you can keep your air conditioner mould-free and enjoy cleaner, healthier air in your home.

When to Call a Professional

While some mould problems in your air conditioner can be handled with regular cleaning, there are times when calling a professional is the safest and most effective option. If you notice a persistent musty smell even after cleaning, or if mould keeps coming back, it could be a sign of a deeper issue within the unit.

Visible mould spreading across vents, coils, or deep inside the ductwork is another red flag. Without proper tools and expertise, DIY cleaning may not be enough to remove mould completely, and disturbing it could even release more spores into the air.

If you or your family members are experiencing frequent allergies, respiratory issues or unexplained headaches, your aircon could be contaminating your indoor air. A professional technician can thoroughly clean and disinfect your system, ensuring mould is completely removed and doesn’t return.

Regular maintenance by an expert can also help prevent mould from forming in the first place. If you’re unsure about the severity of the issue, it’s always best to get a professional inspection.

Don’t Ignore the Signs

Mould in your air conditioner is more common than you might think, but the good news is that it can be prevented and removed with regular maintenance. If you notice musty smells, visible mould or experience allergy-like symptoms when your aircon is running, it’s time to take action. Cleaning your unit, replacing filters and ensuring proper ventilation can help keep mould at bay.

However, if mould keeps coming back or has spread deep inside the system, calling a professional is the safest and most effective solution. Regular check-ups and professional cleaning will not only improve your air quality but also keep your AC running efficiently.

Don’t ignore the signs – taking care of your aircon now will ensure a healthier, fresher home for you and your family.

Please note: This information is provided for advice purposes only. Regulations differ from state to state, so please consult your local authorities or an industry professional before proceeding with any work. See our Terms & Conditions here.