Is the mould in your aircon bad for your health?

What does breathing mould actually do?

Most people know mould is "not great," but not what it actually does. Here's what the major health bodies say — and these aren't our claims, they're theirs.

• The World Health Organization found enough evidence to link damp, mouldy buildings to asthma — both setting off attacks and making it worse — plus coughing, wheezing, breathlessness and chest infections. That's their strongest level of evidence.
• The US EPA says mould can irritate your eyes, nose, throat and lungs — even if you're not allergic to it.
• For people who are allergic, it can bring on hay-fever-type reactions — sneezing, a runny or blocked nose, itchy eyes and skin rashes.

How strong is the evidence, really?

Stronger than most people think. A review that pooled dozens of studies found that damp or mouldy buildings carry roughly a 30–50% higher rate of breathing and asthma problems than dry ones. The WHO put it in their top "sufficient evidence" tier.

The honest bit: that research is about damp, mouldy homes and indoor air in general — not about aircons specifically. So it tells you mould in your indoor air matters; it doesn't prove your unit is behind any one symptom. More on that below.

Who's most at risk?

It hits hardest the people you'd most want to protect. Health authorities single out kids, older people, anyone with asthma or allergies, and people with a weak immune system or a long-term lung condition. If someone in the house ticks one of those boxes, mould in the air is worth being a bit more careful about.

Wait — isn't "toxic black mould" a myth?

Largely, yes — and we'd rather tell you straight than scare you. The idea that mould toxins poison you is overstated. The World Health Organization says the evidence that mould toxins drive indoor-air health problems is "extremely weak," and the US CDC says "toxic mould syndrome" isn't proven.

So no, your aircon isn't going to poison you. The real, well-evidenced problem is the everyday stuff — allergy, irritation, and triggering or worsening asthma. That's reason enough to keep it clean, without the horror-movie framing.

Is my aircon really the problem?

Honestly — it might be one of them. Your aircon is one possible source of indoor mould, not the proven cause of anyone's symptoms. But the inside of a unit is warm, dark and damp, which is exactly what mould likes — and in Townsville's heat and humidity, especially after the wet season, it takes hold fast on the parts you can't see.

Every time the unit runs, it pushes that air through the house. So if the air smells musty when it kicks on, or someone's noticed more sneezing and stuffiness, the aircon is a sensible thing to rule out.

What can you actually do about it?

A few things help keep it down on your own:

• Keep the filters clean — pop them out and rinse them every few weeks in the hotter months.
• Run it on dry or fan mode for a bit after cooling, so the inside isn't left damp.
• Sort out any leaks or damp near the unit, and let the room air out.

Where that stops working: once mould has taken hold on the coil, fan barrel and drain behind the cover, a wipe-over or a spray won't shift it — it just hides the smell for a day or two. That part needs a proper strip-down clean. When we do it, we test and check the unit first, chemical-wash and flush the bits that hold the mould, and send before-and-after photos to your phone. If a unit doesn't actually need it, we tell you — and that one's free.