A dehumidifier is a machine that removes moisture from the air inside a building. It works by pulling humid air through cooling coils where water vapor condenses into droplets, which collect in a tank or drain away. The now-drier air flows back into the room.

You'd use a dehumidifier in damp basements where water seems to hang in the air, making everything feel clammy and cold. In humid climates, dehumidifiers help prevent mold from growing on walls and keep that sticky, uncomfortable feeling out of bedrooms. Books won't get musty, wooden furniture won't warp, and clothes in closets won't develop that damp smell.

Think of it as the opposite of a humidifier, which adds moisture to dry air during winter. If your basement feels like a cool, damp cave even on sunny days, or if you notice condensation forming on windows, a dehumidifier pulls that excess water right out of the air, helping the space feel fresher and preventing damage to your belongings.