A musty or stale smell from an evaporative cooler usually comes from old pads, stagnant water or mould in the unit. Here’s what causes the smell and how a service and good maintenance clear it.
Usually PadsOr stagnant water & mould
Fresh-Air SystemSmells get circulated in
Service FixClean, refresh pads, drain
Why Does It Smell?
An evaporative cooler is, by design, a warm and wet system — it constantly wets pads to cool the air. That moisture, if not maintained, is exactly the environment where stale odours, mould and bacteria develop, in the pads, the tank water and the unit. And because the cooler draws fresh outside air through those wet pads and into your home, any smell in the unit gets circulated indoors. So a musty cooler smell is usually a maintenance issue with a clear fix.
Pads, Water and Mould
The three usual sources are: old pads that have deteriorated and hold odour; stagnant water sitting in the tank (especially if not drained over winter) growing stale; and mould or biofilm in the wet parts of the unit. Hard-water mineral build-up can worsen it. Each is addressable by cleaning and pad replacement. See our mould guide.
How to Clear It
The smell is cleared by replacing tired pads, draining and cleaning the tank to remove stagnant water and sediment, and cleaning the unit to remove mould and biofilm — all part of a service. For a mild stale smell, running the cooler on fan-only to dry it out can help, but a genuine musty or mouldy smell means the pads and unit need cleaning or replacing. See our pad replacement guide.
Preventing the Smell
Prevention is straightforward: replace pads when due, have the cooler serviced (including a tank and unit clean), winterise it by draining so water doesn’t sit stagnant over the off-season, and watch water quality. A pre-season service is the single best step — it starts summer with fresh pads and a clean unit, so the air coming in smells fresh. See our maintenance checklist.
When to Act
Act when you notice a musty, stale or mouldy smell coming through when the cooler runs — especially at the start of the season. The longer a smelly, mould-prone unit runs uncleaned, the more it circulates odours and spores indoors. A service to clean the unit and refresh the pads clears it. If anyone in the home is sensitive to mould, it’s worth addressing promptly. See our winterising guide.
Frequently Asked Questions
Why does my evaporative cooler smell musty?
Because evaporative coolers are warm, wet environments, old pads, stagnant water in the tank, and mould or bacterial growth in the unit can develop a musty or stale smell — and since the cooler draws fresh outside air through those wet pads and into the house, the smell gets circulated indoors. The usual fixes are replacing tired pads, draining and cleaning the unit, and addressing any mould. A service clears it and a clean start to each season prevents it.
How do I get rid of the smell from my evaporative cooler?
The smell is cleared by addressing its source: replacing old, deteriorated pads; draining and cleaning the tank to remove stagnant water and sediment; and cleaning the unit to remove any mould or biofilm. A service does this. Running the cooler on fan-only (without water) for a while can also help dry it out and clear a mild stale smell, but a genuine musty/mouldy smell needs the pads and unit cleaned. See our
pad replacement guide.
Can a smelly evaporative cooler be a mould problem?
Yes — the constant moisture in an evaporative cooler can allow mould and bacteria to grow in the pads, tank and unit if it’s not maintained, and that’s a common source of musty smells. Because the cooler brings outside air through the pads into the home, it can circulate those odours and spores indoors. Cleaning the unit and replacing affected pads addresses it. See our
mould in evaporative coolers guide.
Why does my evaporative cooler smell when I first turn it on for summer?
A stale smell at the start of the cooling season is common — over winter, residual moisture, old pads and sediment can develop a musty odour that’s noticeable on first use. This is exactly why a pre-season service (fresh pads, a clean and a check) is worthwhile: it starts the season clean and smell-free. If the smell persists after first use, the pads and unit need cleaning or replacing.
How do I stop my evaporative cooler smelling in future?
Keep it maintained: replace pads when they’re due, have the unit serviced (which includes cleaning the tank and unit), winterise it properly by draining it so water doesn’t sit stagnant over the off-season, and keep an eye on water quality, since mineral build-up and stagnant water contribute. A clean, well-maintained cooler with fresh pads brings in fresh-smelling air. See our
maintenance checklist.
Evaporative Cooler Problem or Service? Talk to FreshDuct
Service, pad replacement, repairs & installation across Melbourne — 7 days a week. Call or request a quote.
