Switch on the AC after a few weeks off and the room smells like a wet cellar for a minute? That smell has an address: the dark, damp interior of your indoor unit, where Malta's humidity and summer dust have been running a mould farm on the coil and blower wheel.
Why Maltese AC units grow mould so readily
An AC in cooling mode is a condensation machine — the coil stays wet all day pulling litres of water out of humid air. Add dust arriving through filters that have not been washed in a while, warm ambient temperatures, and long idle spells (units switched off through mild weeks), and you have textbook mould habitat. Coastal humidity in places like Sliema and San Pawl il-Baħar accelerates it further.
The smell appears at startup because the fan blasts spore-laden damp air off the coil in the first minutes.
Is it a health problem?
It is not something to panic about, and not something to ignore. Mould exposure irritates airways and is a real trigger for asthma and allergy sufferers; a unit that visibly sheds black flecks or smells strongly every startup is circulating spores through the room where you sleep. Households with respiratory conditions, babies or elderly members should treat a mouldy unit as a priority rather than a quirk — it belongs to the same family of problems as our wider guide to damp and mould in Maltese homes.
What actually fixes it
- Not air freshener, and not just rinsing the filters — the colony lives on the coil and the blower wheel behind them.
- A chemical coil clean: the technician opens the unit, applies a coil-safe antimicrobial cleaner, cleans the blower wheel where the black rings live, and flushes the drain tray and line (a blocked, slimy drain usually co-stars — see the leak guide). In Malta this runs €70 to €120 per unit as a deep clean, or less as part of a full annual service.
Keeping it from coming back
- Wash filters monthly through the humid months.
- After heavy cooling days, run fan-only mode for 20–30 minutes before switching off — it dries the coil, removing the standing moisture mould needs. Some modern units do this automatically ("self-clean" modes are mostly exactly this).
- Do not park the unit off for months with a wet interior; give it an occasional fan run.
- Book the annual service in spring so the unit starts summer sterile.
Post the symptoms on Qabbad's AC page — mention the smell, any visible black spots on the vanes, and the unit count — and technicians covering your locality will quote for deep cleans across all units in one visit, which is where the pricing gets sensible.
Frequently asked questions
Why does my AC smell musty when it starts?
Mould and bacteria growing on the wet evaporator coil and blower wheel inside the indoor unit. The startup blast carries the smell into the room until airflow settles.
Is mouldy AC air dangerous?
For most healthy adults it is an irritant rather than a hazard, but for asthma and allergy sufferers it is a genuine trigger. Either way, the fix is cheap enough that living with it makes little sense.
How much does an AC deep clean cost in Malta?
€70 to €120 per unit for a chemical coil and blower clean, with multi-unit discounts common. Bundled into an annual service it often costs less.
Can I clean AC mould myself?
Filters, yes — wash them freely. The coil and blower require opening the unit and using coil-safe chemicals; enthusiastic DIY with household sprays damages fins and electronics. Leave the internals to a technician.