You’ve started to notice it — a musty smell when the air conditioner kicks on. Maybe you’ve seen dark spots near a vent. Or maybe someone in the house keeps sneezing when the AC runs.
If that sounds familiar, mould could be growing inside your HVAC system — and most homeowners have no idea it’s there.
In humid regions like Nowra and the South Coast, it’s not uncommon. Your AC pulls moisture from the air, and if that moisture doesn’t drain properly, it becomes the perfect breeding ground for mould.
At Chilko AIR, we help homeowners deal with this more often than you’d think. Left unchecked, it can affect your health, your energy bills, and your entire system’s performance.
In this article, you’ll learn how to spot the signs early, understand the risks, and know what to do next — including when it’s time to bring in a local pro.
Let’s help you keep your system clean, safe, and running at its best.
What Are the Signs of Mould in Your HVAC System?
Mould in your air conditioning system isn’t always easy to spot — but there are warning signs that shouldn’t be ignored.
Here’s what to look for:
- Musty or damp smells: If your system smells like wet socks or damp carpet when it starts up, mould could be growing on internal components or in the ductwork.
- Black or green spots near vents: Visible discolouration around vents or returns can indicate mould is forming deeper in the system.
- Worsening allergies or respiratory symptoms: If someone in your home experiences sneezing, coughing, itchy eyes or headaches when the AC runs — but not when it’s off — mould could be circulating through the air.
- Unusual condensation: Excess moisture on windows, ducts, or the unit itself may point to poor drainage or airflow issues that encourage mould growth.
- Poor airflow or musty-smelling air: If the air feels stuffy or isn’t circulating well, mould buildup on coils or filters could be restricting the system’s performance.
Not all these signs mean you definitely have a mould problem — but they’re all worth investigating. The sooner you catch it, the easier (and cheaper) it is to deal with.
Is Mould in Your Air Conditioner Dangerous?
In short: it can be — especially if you or someone in your home has allergies, asthma, or a weakened immune system.
Mould spores don’t just stay inside the unit. Once they grow, your AC can push them through your entire home, recirculating contaminated air every time it runs.
Here are some of the health risks associated with mould in HVAC systems:
- Respiratory issues: Breathing in mould spores can trigger coughing, sneezing, or a tight chest — even in people without diagnosed allergies.
- Aggravated asthma: For those with asthma, airborne mould can increase the frequency and severity of attacks.
- Fatigue and headaches: Some people report brain fog, headaches, or constant fatigue when exposed to mouldy environments over time.
- Skin and eye irritation: Itchy eyes, rashes, or sinus irritation can also be linked to indoor mould exposure.
Even if symptoms are mild, prolonged exposure is never a good idea — especially for kids, older adults, or anyone with respiratory conditions.
If you suspect mould, it’s worth getting your system professionally assessed. A clean, well-maintained AC doesn’t just cool your home — it protects your health too.
Chilko AIR can inspect, clean, and restore your AC to safe, efficient operation:
Why Does Mould Grow in HVAC Systems — Especially in Humid Areas Like Nowra?
Mould loves moisture, warmth, and still air — all things your HVAC system can provide if it’s not properly maintained.
Here’s why it’s a particular issue on the South Coast:
- High humidity: Nowra and surrounding areas often experience humid summer days. Even when it’s not raining, the moisture in the air can collect inside ducts, coils, and drip trays.
- Poor drainage: If your system’s condensate drain is blocked or poorly designed, water can sit inside the unit — especially in older systems.
- Dirty filters and coils: Dust and debris act like food for mould. If your filters or coils are clogged, it creates a perfect environment for spores to grow.
- Infrequent use: Holiday homes or rooms that don’t get regular AC use can develop mould faster, especially if ventilation is poor.
- Lack of servicing: Without regular professional maintenance, small moisture issues can go unnoticed — until mould becomes visible or smells become obvious.
The bottom line? Coastal climates are already working against you. That’s why proactive care matters more here than it might in drier inland regions.
Can You Remove Mould Yourself or Should You Call a Professional?
If you see a bit of mould on a vent or grille, it’s fine to wipe it down with a mild cleaner — but that’s just surface-level. The real issue could be deeper inside your system, where DIY won’t cut it.
Here’s when you can handle it yourself — and when you shouldn’t:
You can DIY if:
- The mould is only on accessible external vents.
- You’re cleaning washable filters (and you know how to remove and reinstall them safely).
- You’re using a safe, non-toxic cleaner and wearing protection (mask, gloves).
You shouldn’t DIY if:
- The smell returns after cleaning.
- You see signs of mould inside the indoor unit or ductwork.
- There’s visible water pooling inside or near the system.
- Anyone in your home has experienced recent health symptoms.
Attempting to clean the internal parts of an AC — especially evaporator coils, ducts, or the condensate drain — without proper training can damage your unit or spread spores further.
Chilko AIR offers professional cleaning, drain clearing, and component checks designed specifically for South Coast conditions.
How Do You Prevent Mould from Coming Back?
Once mould is cleaned out of your HVAC system, the next step is just as important: keeping it gone.
Here’s what you can do to prevent it from returning:
- Change or clean filters regularly: Dirty filters reduce airflow and trap moisture and dust — the perfect combo for mould. Most homes should check filters every 2–3 months, especially in summer.
- Book routine maintenance: Annual servicing includes coil cleaning, drain checks, and performance testing. It’s the easiest way to stop small issues (like blocked drains or trapped moisture) from becoming big problems.
- Keep humidity in check: Use exhaust fans when cooking or showering, and open windows when the weather allows. In humid periods, consider running your AC in dry mode or using a dehumidifier.
- Don’t ignore smells: If a musty smell returns, get it checked early. Waiting can lead to more mould — and a more expensive clean-up.
- Install a system designed for humid climates: Some newer split and ducted systems come with self-cleaning features or mould-resistant coils. If your system is outdated, upgrading could save you in the long run.
Chilko AIR offers AC repair and maintenance services tailored to Nowra’s humid climate — helping you stay cool and mould-free:
Mould in your HVAC system isn’t just unpleasant — it can affect your health, comfort, and energy bills. The good news? It’s preventable. If you’re unsure whether your system’s at risk, a quick inspection from a local expert can give you peace of mind.
Chilko AIR is here to help — with honest advice, expert maintenance, and tailored solutions for South Coast homes.