Mould in the air conditioner
- A picture can document visible deposits.
- Colour and appearance do not reliably identify microorganisms.
- The appropriate assessment depends on the issue; a photo is not a laboratory test.
What is really happening
The evaporator stays wet for hours after every stop, at 10–20 °C and with organic dust on the fins: exactly the conditions in which Cladosporium, Aspergillus and Penicillium grow. The black spots on the louver are only the visible part; the main colony is on the blower and in the drain pan.
At start-up a mouldy unit can throw tens of times more spores into the room than there are in outdoor air, and dead spores remain allergenic. That is why we do not recommend 'disinfecting' with a spray over existing mould: it must be washed, then sanitised.
The evidence
Symptom test: does your unit need sanitising?
What to do
Mechanical pressure cleaning of the evaporator, blower and pan inside a collection cover, then sanitising; filters washed every two weeks; room humidity kept between 40 and 60%; the unit dried on fan mode before winter. No sprays over dirt, no bleach in the unit, no refrigerant "top-ups".
Related threads
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Read also
- How much more a dirty unit uses
- Home humidity and air conditioning
- How often to clean and sanitise the air conditioner
- Symptoms of an uncleaned air conditioner
- The air we breathe at home
The information on this page is educational and based on cited sources; it does not replace medical advice. We do not do repairs, installation or refrigerant circuit work.