A Dehumidifier is a piece of equipment used to reduce humidity in an enclosed structure. Dehumidifiers promote faster drying, prevent humidity damage, and help prevent indoor air quality problems. It is simliar to that of of an AC unit, which is further explained here.

How do they Work

Dehumidifiers function by capturing water vapor molecules from the air. A small commercial-grade dehumidifier can extract about three five-gallon buckets a day when the air is extremely saturated with water.

Types of Dehumidifiers

Refrigerant Dehumidifiers are most common. They work by directing moist air over cold refrigerant coils. They are cost effective on highly porous materials such as carpets as well as high humiditys found in the initial stages of a flood. These are quick and easy to install because there is no need to vent reactivation air to the outside. The humidity condenses into a liquid, which the customer is then able to see how much water is being removed from the air. The minimum operating temperature is 50 degrees and these dehumidifiers operate most efficiently above 68 degrees. Most come with defrost systems for cold conditions.

Desiccant Dehumidifiers work by directing moist air over a desiccant material – similar to silica gel. The desiccant is a special material with unique physical properties that attract moisture. There are two types of desiccants:

Absorbent – Change chemically or physically as they absorb water (Lithium or
calcium chloride)
Adsorbent – Do not change chemically or physically as they absorb water. The
most common adsorbent is silica gel. Silica gel absorbs water vapor in its microscopic pores. It can hold a lot of water due to its large surface area.Desiccant dehumidifiers can run in sub-freezing temperatures.