Why does my air conditioning smell?
A new smell from your air conditioning nearly always has a cause you can name. Musty and damp smells usually mean dirt and moisture inside the unit. A burning or hot electrical smell means switch it off now. Here's how to tell them apart and what's safe to do yourself.
- at once for any burning smell
- Switch off
- R32 refrigerant, per Daikin
- Odourless
- filter clean, Daikin and Panasonic
- Every 2 weeks
- annual service, inc. VAT
- £119
What the smell usually means
| The smell | Usual cause | What to do |
|---|---|---|
| Musty, damp or mouldy | Dirty filters, and moisture and dirt on the coil, fan or drain tray | Clean the filters. If it persists, book a clean or service |
| Cooking, smoke, pets or the room itself | Odours soaked up by the unit and blown back out, or a damp smell from walls, carpets or furniture | Clean the filters and air the room. A service cleans the inside |
| Drains or sewage | The condensate pipe may run into your waste plumbing, letting smells travel back | Book a visit so an engineer can check the drain connection |
| Burning, electrical or hot plastic | An electrical part overheating or failing | Switch off at once and book a visit |
| Dusty when first switched on for the season | Dust that settled on the filters and coil while the unit was idle | Clean the filters. If it doesn't clear, book a service |
Why musty smells build up
In cooling, moisture from the room condenses on the indoor coil and drains away. That keeps the inside of the unit damp for part of the year. Dust that gets past dirty filters sticks to the wet coil, fan and drain tray, and that's where musty smells start.
Daikin's manual says a unit with dirty filters can't deodorise the air and causes odour, and that in some conditions the inside of the unit gets dirty after several seasons, which also cuts performance. Panasonic's manual says the coils and fans should be cleaned periodically by an authorised engineer. Filters you can do yourself. The coil, fan and drain need the covers off.
Not every smell comes from the unit. Panasonic's manual notes a peculiar odour can come from damp walls, carpets, furniture or clothing, and Daikin explains that room smells absorbed by the unit are blown back out with the airflow.
Safe things to try
Always stop the unit and switch off the power before cleaning, as Daikin's manual warns of electric shock otherwise.
- Take out the filters and vacuum them, or wash them in lukewarm water with a little neutral detergent. Daikin says not to use water at 40°C or hotter
- Dry the filters in the shade, then refit them before switching back on
- Clean the filters about every two weeks in regular use, as Daikin and Panasonic both recommend
- Check your manual for any extra deodorising filter. Some Daikin models have one that's washed every six months and replaced every three years
- Wipe the casing and front panel with a soft, damp cloth
- Air the room well, especially after cooking or decorating
- Before a long idle spell, dry the inside: Daikin suggests running fan only, and Panasonic suggests heat mode for two to three hours
- Clear leaves and debris from around the outdoor unit
What not to do
Shop-bought sprays and foams promise a quick fix, but they can damage the unit and rarely reach the source of the smell.
- Don't spray bleach, disinfectant, air freshener or foam cleaner into the unit. Daikin warns against solvents, polishes and insecticide
- Don't take off covers to reach the coil, fan or drain tray. Daikin says inside parts must be cleaned by a qualified service person
- Don't touch or brush the coil fins. They're sharp and bend easily
- Don't keep running the unit if it smells of burning, even if the smell fades
- Don't try to open the refrigerant pipes. That's restricted by law to F-Gas certified engineers
Can you smell a refrigerant leak?
Usually not. Daikin's manual states that R32, the refrigerant in many current home systems, is odourless. So a chemical smell is more likely to be something in the room or a part getting hot. Treat a hot plastic smell as a burning smell and switch off.
A refrigerant leak normally shows up as poor cooling or heating, ice on the pipes or an error code. If you suspect one, Daikin advises turning off any flame or heater in the room, airing the room and calling an engineer, because R32 is mildly flammable.
What it costs to sort out
Most musty smells are cured by a full service, which cleans the inside of the unit. For a burning or drain smell, book a diagnostic visit, which we take off the bill if you go ahead with the repair.
- from£119inc. VAT
An annual service
Keeps the manufacturer warranty valid
- from£125inc. VAT
Repair diagnostic visit
First hour on site, deducted if you go ahead
Air conditioning smell questions
Why does my air conditioner smell musty?
Moisture and dust build up on the coil, fan and drain tray inside the indoor unit, often helped by dirty filters. Clean the filters first. If the smell stays, the inside needs a professional clean, which is part of a full service.
Why does my air con smell of burning?
It can mean an electrical part is overheating. Switch the unit off at the isolator or fused spur, don't use it again, and book a visit. Daikin's manual gives the same advice. If there's smoke or fire, call 999.
Why does my air conditioning smell like drains?
If the condensate pipe runs into your waste plumbing, smells can travel back up it and out through the unit. An engineer can check how the drain is connected and put it right.
Can I spray disinfectant into my air conditioner?
No. Manufacturers warn against chemicals inside the unit, and sprays can damage parts without reaching the dirt causing the smell. Clean the filters yourself and leave the coil, fan and drain to an engineer.
Does air con refrigerant have a smell?
R32, used in many current home systems, is odourless according to Daikin. A leak usually shows as poor cooling, ice on the pipes or an error code rather than a smell.
Will a service get rid of the smell?
For musty and damp smells, usually yes. Our service includes cleaning the indoor coil, fan and air outlet, flushing the drain and tray, and cleaning the filters. Burning and drain smells need a repair visit instead.