There are two types of dehumidifiers:

  1. Compressor/refrigerator type dehumidifiers
  2. Desiccant dehumidifiers (works at lower temperatures)

A compressor/refrigerator type dehumidifier takes the moisture from the surrounding air, thereby lowering the humidity. It does this by condensing water on a cold surface. It is a similar principle to water collecting on the outside of the glass of a cold drink on a hot day. The fan within the dehumidifier pulls the humid air from the surrounding room into the dehumidifier. This air passes across a cold coil. The humidity within the air condenses and the water which is created drips into a drain or container. The resulting cold air is passed over a warm coil to bring it back to room temperature.

A desiccant dehumidifier work using an adsorption agent like silica gel. The gel is applied in honeycomb form to an anorganic fleece - the drying wheel. The porous structure of the drying wheel provides an extraordinarily large surface area covering approx. 2,000 metres cubed. Rotation of the drying wheel allows adsorption and regeneration to occur in a continuous cycle, so the air is dehumidified.