In systems involving heat transfer, a condenser is a heat exchanger used to condense a gaseous substance into a liquid state through cooling. In doing so, the latent heat is released by the substance and transferred to the surrounding environment. Condensers are used for efficient heat rejection in many industrial systems. Condensers can be made according to numerous designs and come in many sizes ranging from rather small (hand-held) to very large. For example, a refrigerator uses a condenser to get rid of heat extracted from the interior of the unit to the outside air.