What does mold smell like?

Most people describe it as musty, earthy, or like wet cardboard and a damp basement. The smell can be stronger when the air conditioner starts, when you open a closet, or the day after rain. A sharp smell that fades when you leave the house is worth chasing.

Musty does not always mean visible mold. It can be damp dust, a dry trap, or a coil pan. Start with the basement, the air handler, and the attic hatch before you buy a stack of air samples.