Bacteria and fungi colonize a coil that stays damp, and the smell is strongest when the system starts or when a heat pump comes out of defrost and warms the wet coil. It is common in humid climates and in homes with oversized or short-cycling equipment. Cleaning the coil and drain pan with an appropriate coil cleaner, improving drainage and sometimes UV lamps are the usual fixes.
Customer says the house smells like a locker room every time the heat pump kicks on, classic dirty sock syndrome.
Also heard as
- DSS
- dirty sock smell
Related terms
Heat pump
A refrigeration system that can reverse its flow to move heat indoors in winter as well as outdoors in summer.
Evaporator
The coil or heat exchanger where low-pressure liquid refrigerant boils off, absorbing heat from air or water.
Drain pan
The pan under a cooling coil that catches condensate and routes it to a drain line.
IAQ
Indoor air quality: how clean and healthy indoor air is, judged by contaminants, ventilation, humidity and comfort.