Home health and air conditioning

What happens inside an uncleaned air conditioner and what it means for the air you breathe, explained in plain language, with cited studies.

Woman on the sofa noticing the unpleasant smell when switching the air conditioner on

Bad smell from the air conditioner

The 'cellar', 'wet socks' or sour smell at start-up is not dust: it is the metabolic product of the bacteria and mould living in the biofilm…

Louver of the unit with black mould spots on the edge, before sanitising

Mould in the air conditioner

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 Cladospo…

Indoor coil black with deposits seen through the cover before washing

Bacteria in the air conditioner

Measurements in apartment units show loads of thousands to tens of thousands of colony-forming units per square centimetre in the drain pan,…

Man at his desk rubbing irritated eyes under the air conditioner

Allergies, sneezing and irritated eyes from the air conditioner

Irritation and sneezing can have different causes. Inspecting the unit and indoor conditions may help, while persistent symptoms should be discussed with a clinician.

Baby sleeping in the crib while the mother checks the hygrometer, clean unit on the wall

Air conditioning and small children

Babies and small children have narrow airways, breathe faster and spend most of their hours in the bedroom, in the path of the unit. Meta-an…

Mother feeling her child's forehead in bed, air conditioner above

Asthma, bronchitis and air conditioning

A clean air conditioner is an ally for an asthmatic: it filters coarse dust and lowers the humidity and temperature that trigger attacks. A …

Woman breathing in relaxed the clean air in the kitchen, with the sanitised unit on the wall

The air we breathe at home

We spend 90% of our time indoors, and in summer room air passes through the air conditioner several hundred times a day. Whatever lives on t…

Dust and lint visible in the beam of light coming out of the unit's louver

Symptoms of an uncleaned air conditioner

You see them, smell them or pay for them: smell at start-up, dust leaving the louver in the light beam, black spots on the edge, weak airflo…

Washed filters left to dry on a white towel by the window

How often to clean and sanitise the air conditioner

Manufacturers (Daikin, Mitsubishi Electric, LG, Panasonic) say the same in their manuals: filters washed every two weeks in season, and inte…

Cover fitted on the unit, hose running neatly into the white bucket, spotless living room

Sanitising with a cover bag or by dismantling?

The collection cover is a double-layer waterproof sheet sealed around the indoor unit and ending in a drain hose; it allows pressure washing…

Coil fins full of dust and fluff, before cleaning

How much more a dirty unit uses

US Department of Energy data: a dirty filter raises consumption by 5–15%. Lawrence Berkeley Laboratory measured that coil pressure drop doub…

Hygrometer on the nightstand in a bedroom with the clean unit

Home humidity and air conditioning

Air conditioning dries the air, which is good up to a point: below 40% humidity mucous membranes get irritated, above 60% dust mites multipl…