Bacteria in the air conditioner
- A typical split recirculates room air.
- Ventilation introduces outdoor air through a suitable solution.
What is really happening
Measurements in apartment units show loads of thousands to tens of thousands of colony-forming units per square centimetre in the drain pan, on filters and on fins, far above what is considered clean. The Methylobacterium biofilm on aluminium resists drying and UV, so it does not go away on its own.
The good news, confirmed by the CDC: home units do not use water for cooling, so they are not a Legionella source; anyone selling sanitising with the fear of Legionnaires' disease is exaggerating. The realistic news: bacteria and mould in the unit sustain smell, allergies and irritation, and professional cleaning reduces them by over 99%.
The evidence
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".
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Read also
- Symptoms of an uncleaned air conditioner
- Sanitising with a cover bag or by dismantling?
- How often to clean and sanitise the air conditioner
- Mould in the air conditioner
- How much more a dirty unit uses
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.