🗓 Updated July 24, 2026 · EcoBack editorial team
A portable air conditioner is a dust magnet with a wet interior — the perfect combination for clogged filters, limescale and, eventually, mould. The good news: everything you need to clean is reachable without tools, and the whole routine takes about twenty minutes. This guide covers each part in the order you should do them, plus an honest section on mould: what vinegar genuinely handles, and where you should stop.
Compiled from public tests & customer reviews — not tested by us. Prices vary; check the current price on Amazon. Illustrations, not product photos.
De'Longhi Pinguino PAC EX105
Strong cooling, often in the test-winner line.
Comfee MPPH-09CRN7
Affordable for small bedrooms & offices.
It draws in warm room air, cools it and returns it — the waste heat leaves through the window hose. Real cooling, not just moving air around.
Why cleaning matters: cooling power, smell, mould
Three separate problems trace back to the same neglected maintenance. First, cooling power: a dust-clogged filter chokes the airflow over the cold coil, so the unit cools less while drawing the same electricity — and in bad cases the coil ices over and cooling collapses entirely. Second, smell: condensate and damp dust inside the housing grow a bacterial film that makes the outlet air smell musty within weeks. Third, mould: leave that film long enough in a dark, wet interior and it becomes visible mould growth — a health issue, not just a comfort one.
The cause chain matters because it tells you what actually works: cleaning removes the dust (the food), and drying removes the moisture (the habitat). Do both and the problems stay away; do only one and they come back.
Filter cleaning, step by step
The filter is the highest-impact five minutes of the whole routine. Manufacturers typically recommend cleaning it every one to two weeks during regular use — more often if you have pets.
- Unplug the unit. Always, before any cleaning step.
- Slide the filter out. It sits behind the intake grille on the back or side; on most models it releases without tools.
- Vacuum the loose dust with a brush attachment, working from the clean side outwards.
- Rinse in lukewarm water. Not hot — heat can warp the plastic frame. For greasy film (kitchens), a drop of washing-up liquid is fine. No harsh cleaners.
- Air-dry fully. This is the step people skip. A damp filter refitted into a dark housing is a mould starter kit. Stand it upright somewhere ventilated until it is bone dry, then refit.
If your unit has a separate secondary filter (some models pair the mesh pre-filter with a carbon or fine-dust insert), check the manual: the mesh part is washable, but carbon inserts usually cannot be washed and are replaced instead.
Water tank and drain
The internal tank and drain channel collect condensate all season, and standing water leaves two things behind: limescale and a slippery biofilm. Both come off with the same treatment:
- Drain the tank completely via the plug low on the back of the unit.
- Fill or rinse it with a 50/50 mix of white vinegar and water, let it sit for around 30 minutes, then scrub reachable surfaces with a bottle brush.
- Rinse thoroughly with clean water until the vinegar smell is gone, and leave the drain plug out until the channel has dried.
While you are down there, check that the drain outlet is clear — a blocked or gunked-up drain is one of the classic causes when a portable AC starts leaking water onto the floor instead of collecting or evaporating it.
Coils and housing
Behind the filter sit the evaporator coils with their thin aluminium fins. Dust that gets past the filter settles here, and because the coil is wet during operation, it settles as a stubborn damp layer.
Work gently: the fins bend if you look at them wrong. Use a soft brush (a clean paintbrush works well) or a vacuum with a soft brush head, stroking along the fins, never across them. For a grimy coil, a purpose-made no-rinse AC coil cleaner spray foams into the fins and drips out through the condensate channel — do not improvise with kitchen sprays, which can corrode aluminium.
The housing itself just needs a wipe with a damp cloth, plus a vacuum pass over the intake and outlet grilles. Never hose down or submerge any part of the unit, and keep liquids away from the control panel.
Mould: when vinegar is enough — and when to stop
Honesty section. Vinegar is a reasonable household helper against light, surface-level growth on smooth, reachable parts: the tank, the drain channel, a removable grille. Wipe, let it sit, rinse, dry.
It is not the answer when mould is established inside the unit — visible fuzzy patches on the coil or inside ducting you cannot reach, or a mouldy smell that returns days after every clean. Porous deposits and fin gaps protect the growth, and half-killing it just means breathing spores in the meantime. At that point the defensible options are a disinfectant coil cleaner that is actually registered for the job (in the US that means EPA-registered; in the EU, look for an approved biocidal product designation, not a generic "fresh scent" spray) — or, on a budget unit with heavy internal growth, replacing the machine. That is not a sales pitch; it is the same conclusion consumer advice bodies generally reach, because a full internal strip-down costs more in time or fees than a basic monobloc is worth.
If your problem is smell rather than visible growth, start with the dedicated walkthrough in portable AC smells musty — most odour cases are fixable without any biocide at all.
How often should you clean each part?
Frequencies below reflect what manufacturers typically recommend in their manuals; shorten them if you run the unit around the clock, have pets, or live somewhere dusty.
| Part | How often | Method |
|---|---|---|
| Air filter | Every 1–2 weeks in season | Vacuum or lukewarm rinse, air-dry fully |
| Water tank & drain | Monthly, plus at season end | 50/50 white-vinegar rinse, 30 min, rinse well |
| Coils & fins | 1–2× per season | Soft brush along the fins; coil cleaner if grimy |
| Housing & grilles | Monthly | Damp cloth, vacuum the grilles |
| Interior drying (fan-only run) | After every cooling session | 15–30 min fan mode until the coil is dry |
Before storage: the autumn shutdown
How you put the unit away in autumn decides what greets you next June — a clean machine or a mould smell you cannot shift. The end-of-season routine:
- Drain everything. Open the drain plug and empty all condensate, tilting the unit slightly if the manual allows it.
- Run fan-only mode for about an hour so the coil and the interior dry out completely.
- Clean the filter one last time and refit it only once fully dry.
- Detach the exhaust hose, let it dry, and store it separately so no trapped moisture sits in the folds.
- Store upright, ideally in the original box or under a breathable cover — not airtight plastic wrap, which traps residual humidity.
Storing it upright matters for the compressor too: portable ACs should not overwinter lying on their side.
Frequently asked questions
How often should I clean a portable air conditioner filter?
During daily use in a heatwave, every one to two weeks — manufacturers typically recommend the same interval in their manuals. If the unit only runs occasionally, once a month is enough. The filter sits behind the intake grille and slides out without tools on most models: vacuum it or rinse it in lukewarm water, let it air-dry completely, then put it back.
Can I clean a portable air conditioner with vinegar?
Yes, for the water tank, drain outlet and light surface deposits: a 50/50 mix of white vinegar and water dissolves limescale and slime, left to sit for about 30 minutes and rinsed well. Do not pour vinegar over the coils or electronics, and do not rely on it for established mould growth inside the unit — for that, use an EPA-registered (or EU-approved biocidal) coil cleaner, or accept that the unit may need professional cleaning or replacement.
Why does my portable air conditioner still smell after cleaning?
Usually because moisture was left inside. The evaporator coil stays wet after cooling, and if the unit is switched straight off, that damp darkness is exactly where odour-causing film regrows within days. Run fan-only mode for 15 to 30 minutes after every cooling session so the coil dries out. If the smell survives a full clean plus the fan-dry habit, mould has likely established itself deeper inside the housing than you can reach.
How do I stop mould growing in a portable air conditioner?
Keep it dry. Empty the internal tank regularly, run fan-only mode after cooling so the evaporator dries, and clean the filter every one to two weeks so dust never builds up as a food source. Before storing the unit for winter, drain all condensate, run the fan for about an hour and store it upright with the hose detached — a fully dry machine stays mould-free.