Humidity
Air conditioning equipment usually reduces the humidity of the air processed by the system. The relatively cold (below the dew point) evaporator coil condenses water vapor from the processed air , much as cold drink will condense water on the outside of a glass. The water is drained , removing water vapor from the cooled space and thereby lowering its relative humidity. Since humans perspire to provide natural cooling by the evaporation of perspiration from the skin , drier air (up to a point) improves the comfort provided. The comfort air conditioner is designed to create a 40% to 60% relative humidity in the occupied space. In food retail establishments , large , open chiller cabinets act as highly effective dehumidifiers.
Some air conditioning units dry the air without cooling it. These work like a normal air conditioner , except that a heat exchanger is placed between the intake and exhaust. In combination with convection fans , they achieve a similar level of comfort as an air cooler in humid tropical climates , but only consume about one-third the energy. They are also preferred by those who find the draft created by air coolers uncomfortable.