"Dehumidify"

A dehumidifier is an air conditioning device which reduces and maintains the level of humidity in the air. This is done usually for health or thermal comfort reasons or to eliminate musty odor and to prevent the growth of mildew by extracting water from the air. It can be used for household, commercial, or industrial applications. Large dehumidifiers are used in commercial buildings such as indoor ice rinks and swimming pools, as well as manufacturing plants or storage warehouses. Typical air conditioning systems combine dehumidification with cooling, by operating cooling coils below the dewpoint and draining away the water that condenses.

Dehumidifiers extract water from air that passes through the unit. There are two common types of dehumidifiers: condensate dehumidifiers and desiccant dehumidifiers, and there are also other emerging designs.

Condensate dehumidifiers use a refrigeration cycle to collect water known as condensate, which is normally considered to be greywater but may at times be reused for industrial purposes. Some manufacturers offer reverse osmosis filters to turn the condensate into potable water.

Desiccant dehumidifiers (known also as absorption dehumidifiers) bond moisture with hydrophilic materials such as silica gel. Cheap domestic units contain single-use hydrophilic substance cartridges, gel, or powder. Larger commercial units regenerate the sorbent by using hot air to remove moisture and expel humid air outside the room.

An emerging class of membrane dehumidifiers, such as the ionic membrane dehumidifier, dispose of water as a vapor rather than liquid. These newer technologies may aim to address smaller system sizes or reach superior performance.

The energy efficiency of dehumidifiers can vary widely.