Why mould loves South-East Queensland (and your split system air conditioner)

Brisbane and the Redlands are warm and humid for big chunks of the year. That combo encourages mould to grow—especially inside split-system air conditioners where it’s dark, damp and full of dust to feed on.

Common mould triggers in splits

• High humidity after rain or during summer storms. Moist air condenses on your indoor coil, leaving surfaces moist long enough for mould spores to take hold.

• Clogged or dusty filters restricting airflow. When the fan can’t move enough air, the coil gets colder and wetter, creating the perfect breeding ground for mould.

• Wet drain pans and drains that don’t fully clear. Stagnant water sits in the pan and line, allowing biofilm and odours to develop and then recirculate through the room.

• Short, stop-start cooling cycles that never dry the coil and fan barrel. Frequent cycling leaves moisture in the system, so it never gets a chance to purge humidity properly.

• Closed-up rooms with little ventilation. Still air traps moisture and stops the system from drying out between cooling runs.

Why it matters

• Musty odours the moment you switch on. That “dirty socks” smell is often microbial growth being pushed off the coil and fan into your living space.

• Reduced cooling efficiency and higher power bills. Mould and dust act like a blanket over coils and filters, forcing the unit to work harder for the same result.

• Visible dark growth on louvers or behind the fascia. If you can see it at the front, there’s usually more hiding on the fan barrel and coil fins inside.

• Aggravated allergies or asthma for sensitive people. Spores and fine particles can irritate airways, which is the last thing you want during a humid Brisbane summer.

The Brisbane split-system hygiene plan | Quick wins you can do today

Set up your unit to stay drier

• Use “Dry” mode on muggy days to strip moisture without over-cooling. This mode prioritises dehumidification, which helps prevent mould from getting established.

• Aim for 24–25 °C when cooling so the system doesn’t over-condense. A moderate set-point keeps you comfortable while reducing unnecessary moisture on the coil.

• Run the fan for 10–15 minutes after cooling to help dry internal parts. A brief after-run clears residual moisture from the coil and fan barrel so they don’t stay damp.

• Ventilate the space whenever practical. Use exhaust fans after showers and cooking, and crack a window on pleasant evenings to purge humid indoor air.

A monthly 10-minute filter routine

• Power the unit off at the remote and let the fan stop completely. This keeps you safe and stops dust being drawn in while you work.

• Lift the fascia and slide out the mesh filters carefully. Most splits make this easy, and you won’t need tools for standard filter access.

• Vacuum or rinse with lukewarm water until the mesh looks clear. Avoid hot water and harsh chemicals, then allow the filters to dry fully so you don’t re-introduce moisture.

• Wipe the fascia and louvers with a soft, damp cloth. A mild detergent is fine for plastics and will remove light grime that feeds mould.

• Set a calendar reminder for every 2–4 weeks in summer and monthly in shoulder seasons. Regular attention keeps airflow strong and odours at bay.

When DIY stops and pro servicing starts | Signs you need a professional clean and inspection

Call us if you notice

• A musty or “dirty socks” smell on start-up that lingers. This usually points to microbial growth on the coil or fan that basic filter cleaning won’t remove.

• Water leaks from the indoor head or staining on the wall. Blocked drains or a mis-level unit can cause overflow, which needs prompt attention to avoid damage.

• Visible growth on the fan barrel, coil or behind the fascia. If contamination is visible, a strip-down clean and sanitise is the safest, most effective fix.

• Rattles, grinding or squeals from the indoor or outdoor unit. Noises can indicate worn bearings, loose mounts or debris in the fan that should be addressed early.

• Poor cooling despite clean filters and correct settings. Low refrigerant, dirty coils or electrical faults can all cut performance and push up energy use.

What’s included in a proper Brisbane service

• Coil clean and sanitise for both indoor and outdoor units. HVAC-safe products dissolve grime and biofilm so heat can transfer efficiently again.

• Fan barrel clean to remove stubborn build-up. This step tackles the hidden mould on the rotating drum that commonly causes odours.

• Condensate drain flush so water clears properly. A clear drain prevents leaks, smells and the return of mould in the pan and line.

• Refrigerant pressure and electrical checks for efficiency and safety. Correct charge and sound connections protect the compressor and keep running costs down.

• Airflow measurement and thermostat calibration for even room temps. Tuning the system ensures it cools quietly and maintains comfort with minimal energy.

We service the locals including Thornlands, Cleveland, Capalaba, Victoria Point, Wynnum-Manly and across Brisbane. Book your annual air con service and clean before the first heatwave.

Deep hygiene | getting rid of the musty smell for good

Indoors

• Keep surfaces and carpets dry, and fix plumbing leaks promptly. Persistent dampness feeds mould colonies, which then spread into your AC when it runs.

• Block direct sun on west-facing rooms to cut afternoon heat load. Less heat means shorter cooling cycles and fewer opportunities for condensation to linger.

• Add ceiling fans to move air so the split can dry itself faster. Gentle air movement boosts comfort and helps the system purge residual moisture.

• Consider a dehumidifier in persistently damp rooms. In problem spaces, a standalone unit can lower background humidity so the AC stays cleaner.

At the outdoor unit

• Maintain 300–500 mm clearance around the condenser. Adequate space lets hot air escape, improving efficiency and reducing strain on components.

• Clear leaves, check the insulation on the refrigerant lines, and ensure the slab or brackets are level. Good airflow and firm mounting reduce noise, corrosion and energy waste.

• If you’re bayside, ask about corrosion-resistant coatings. Salt-laden air in the Redlands and coastal suburbs can attack fins and fasteners without protection.

Solar-smart mould prevention (SEQ special)

• Use your midday solar to pre-cool and dehumidify living areas. Running hygiene cycles while the sun is out costs less and leaves the unit drier going into the evening.

• Run “Dry” or a gentle “Cool” on sunny afternoons so the coil stays clean. Lower indoor humidity slows mould growth and helps maintain that fresh, neutral smell.

• Thinking about getting solar panels or battery storage installed in Brisbane? Get in contact with us today for a free quote

Safety first (read this before any DIY)

Electrical

• Never hose or spray the indoor unit under any circumstances. Water and electronics don’t mix, and you can damage sensors or cause a short.

• If you’re removing covers or working near wiring, switch off at the isolator or switchboard. When in doubt, don’t proceed—call a licensed electrician near me for help.

Cleaning

• Use mild detergent or HVAC-approved cleaners on plastics and fins. Harsh chemicals can corrode metals and degrade plastics, creating more problems later.

• Do not mix household chemicals such as bleach and ammonia or vinegar. Some combinations release dangerous fumes that can harm your health and your AC.

• Wear gloves and eye protection when using any cleaner. Simple PPE prevents irritation from splashes and keeps the job comfortable.

• If mould is extensive or returns quickly, book a professional clean. Recurring contamination points to internal build-up or drainage issues that need proper service.

If your switchboard is old or lacks safety switches, a switchboard upgrade in Brisbane and Redlands improves protection for high-load appliances like air con and keeps your home compliant.

Seasonal checklist for Brisbane & Redlands | (Spring (before the sticky weather)

• Full professional service and clean

• Test Dry mode and timer schedules

• Replace tired remote batteries

Filters every 2–4 weeks

• Fan after-run for drying

• Pre-cool on solar afternoons

Autumn (post-storm tidy-up)

• Check for leaks, staining, odours

• Clear debris from the outdoor unit

• Book any repairs before winter (bearings, noisy fans, controls)

Got an older split that’s a repeat offender for mould or odour? Talk to us about an efficient air conditioner installation. We also handle solar repairs in Brisbane if your PV isn’t pulling its weight.

FAQs – Air con mould & hygiene (Brisbane)

Brisbane and the Redlands are tough on air conditioners—but with smart settings, simple habits and a yearly service, your split system can stay clean, efficient and fresh all summer. Solair Electrical can help with air con maintenance and installation.