What a musty smell is
- The gas given off by mould and bacteria growing on something damp. If you can smell it, growth is under way somewhere above 60% relative humidity, seen or not.
- Air fresheners cover the smell. They do not touch the source.
Finding the source, room by room
- Strongest when the AC starts: the evaporator coil, drain pan or duct lining. Technicians note that moisture builds inside a system left off for weeks.
- Bedroom: open the wardrobe and smell the shoes and cotton first, then the mattress and the wall behind the headboard.
- Kitchen and bathroom: under the sink, behind the washing machine, silicone joints.
- Living room: behind sofas and bookcases on external walls, under rugs.
Removing it for good
- Fix any leak and dry the wet material.
- Clean hard surfaces with detergent, wash textiles hot, discard porous items that still smell after two washes.
- Have the AC coil and drain pan cleaned if the smell comes from the vents.
- Bring indoor humidity to 45–55% and keep it there with a ducted dehumidifier against musty odours and damp wardrobes. Carbon filtration in the same unit removes the residual odour.
Where this applies
