How to Check for Mould in Air Conditioners

Mould in your air conditioner is more than just an unpleasant sight or smell – it can affect your health and your home’s comfort.

Because air conditioners circulate air throughout your house, any mould inside the unit can easily spread, leading to allergy symptoms, respiratory irritation, and poor indoor air quality.

It can also cause your system to work harder, reducing efficiency and driving up energy costs. The good news is that spotting mould early isn’t difficult if you know what to look for.

By taking a few minutes to check your unit regularly, you can prevent small problems from turning into big ones. In this guide, we’ll show you simple steps to check for mould in your air conditioner.

Why Mould Grows in Air Conditioners

Air conditioning systems create the perfect environment for mould to thrive. Whenever your system cools warm air, condensation forms inside the unit. This constant presence of moisture, especially in areas like the drip tray, coils and filters, makes it easy for mould spores to settle and grow.

Add a little dust or organic debris, and you’ve provided mould with the food source it needs to multiply.Poor ventilation is another common culprit. If air doesn’t circulate properly through the unit, damp spots can linger, creating the ideal breeding ground for mould.

Similarly, clogged filters or blocked drainage systems allow water to pool, which encourages growth. In homes located in humid climates, the risk increases even more, as air conditioners work harder and collect more moisture.

Once mould takes hold, it not only spreads quickly inside your system but also circulates spores through your indoor air. This can lead to musty smells, reduced efficiency and even health issues.

Regular cleaning and maintenance are key to stopping mould before it becomes a serious problem.

Warning Signs of Mould in Your Air Conditioner

Mould in your air conditioner often makes itself known before you actually see it. Knowing the early warning signs can help you act quickly and prevent bigger issues.

Here are some key indicators to look out for:

• Musty or damp odours – If your air conditioner gives off an earthy, stale smell whenever it’s running, mould could be the culprit.
• Visible spots or discolouration – Black, green or brown patches around vents, filters, or drip trays are clear signs of mould growth.
• Increased allergy symptoms – Frequent sneezing, coughing, watery eyes, or even headaches when the AC is on can be a reaction to mould spores in the air.
• Poor airflow – Mould can clog filters and air ducts, making your system less effective at cooling.
• Condensation or standing water – Excess moisture inside the unit often leads to mould if left unchecked.

Spotting these signs early allows you to take action, protect your indoor air quality, and keep your system mould free and running smoothly, from split systems to ducted air conditioners.

Step-by-Step Guide: How to Check for Mould

Checking your air conditioning unit for mould doesn’t have to be complicated. With a little care and the right approach, you can spot issues before they affect your health and comfort.

Here’s a simple step-by-step guide:

1. Turn off and unplug the unit – Always start by switching off the power to ensure your safety.
2. Inspect air vents and grills – Look closely for black, green, or brown spots around the vents where air flows out.
3. Remove and check the air filter – If it smells musty or shows visible mould growth, it’s time to replace it.
4. Examine the drip tray and drainage system – Standing water is a breeding ground for mould. Make sure it’s clear and draining properly.
5. Shine a flashlight inside the coils and ducts – Mould often hides in darker, harder-to-reach spots.
6. Trust your nose – A persistent, earthy odour is a strong indicator even if mould isn’t visible.

By following these steps, you can catch mould early and prevent it from spreading throughout your home. Be sure to check both the indoor unit and outdoor unit.

Tools and Safety Precautions to Use

When checking for mould in your air conditioner, safety should always come first. Mould spores can cause irritation and health issues, so taking the right precautions makes the process much safer and more effective.

Here are some essentials to have on hand:

• Protective gear – Wear disposable gloves, a face mask, and safety glasses to avoid direct contact with mould and to reduce inhalation of spores.
• Flashlight – Helps you spot hidden mould in dark areas like air ducts, coils and drip trays.
• Cleaning cloths or wipes – Useful for wiping down surfaces during your inspection.
• Mild cleaning solution or vinegar spray – Handy if you need to remove small amounts of mould on accessible surfaces.
• Garbage bags – For safely disposing of contaminated filters, wipes or rags after cleaning.
• Step ladder – If your unit is wall-mounted, a ladder makes it easier and safer to access vents and air filters.

By using these tools and precautions, you’ll not only protect yourself but also ensure a thorough and safe inspection of your air conditioner.

What to Do if You Find Mould

Discovering mould in your air conditioner can feel overwhelming, but it’s important to act quickly to stop it from spreading. If the mould is only on the surface of vents, grills or filters, you can usually handle it yourself.

Start by turning off and unplugging the unit. Wear gloves, a mask, and safety glasses to protect yourself from spores. Remove and dispose of any contaminated filters, then clean the affected surfaces with a mild detergent, white vinegar solution, or a specialised mould cleaner.

For mould deep inside the system – such as coils, ducts or drainage trays – it’s best to call a licensed heating, ventilation and air conditioning (HVAC) technician.

They have the tools and expertise to safely remove mould and prevent it from coming back. Avoid using bleach inside your unit, as it can damage components and doesn’t always kill mould completely.

Once cleaned, keep up with regular maintenance, such as changing filters, clearing drainage lines, and scheduling professional servicing. Acting promptly ensures a healthy indoor environment and a more efficient air conditioner.

How to Prevent Mould in the Future

Once you’ve dealt with mould in your AC unit, the next step is keeping it from coming back. Prevention is much easier than tackling a mould outbreak, and it also helps your unit run more efficiently.

Here are some simple ways to stay ahead of the problem:

• Clean or replace filters regularly – Dirty filters trap moisture and dust, giving mould exactly what it needs to grow.
• Keep the drip tray and drain line clear – Make sure water flows away properly so it doesn’t pool inside the unit.
• Schedule professional servicing – A licensed technician can clean deep inside the system where mould thrives.
• Use a dehumidifier in humid weather – Lowering indoor humidity makes your air conditioner less likely to collect excess moisture.
• Improve ventilation – Keep rooms well-aired so damp air doesn’t linger.
• Run your unit regularly – Stagnant air and moisture can build up if the system isn’t used for long periods.

By following these steps, you’ll enjoy cleaner, fresher air and a healthier home environment.

Catch the Signs Early

Mould in your air conditioner isn’t something you want to ignore. Left unchecked, it can spread quickly, compromise your indoor air quality, and even affect your health.

The good news is that with a little awareness and regular maintenance, you can catch the signs early and prevent mould from becoming a major issue. Simple steps like checking filters, keeping drainage lines clear and scheduling routine servicing go a long way in protecting your home.

If you do spot mould, act promptly – clean what you can safely and call a professional for more serious cases. By staying proactive, you’ll not only keep your air conditioner running efficiently but also enjoy fresher, cleaner air throughout your home.

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.