An Air Conditioner (often referred to as AC) is a system designed to dehumidify and extract heat from an area. The cooling is done using a simple refrigeration cycle. The definition of cold is the absence of heat and all air conditioner systems work on this basic principle. Heat can be removed through the process of radiation, convection, and heat cooling through a process called the refrigeration cycle.Refrigeration 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, sending the water to a drain and removing water vapor from the cooled space and lowering the relative humidity.

An evaporative cooler is a device that draws outside air through a wet pad, such as a large sponge soaked with water. The sensible heat of the incoming air, as measured by a dry bulb thermometer, is reduced. The total heat (sensible heat plus latent heat) of the entering air is unchanged.

HVAC is an acronym that stands for the closely related functions of “Heating, Ventilating, and Air Conditioning the technology of indoor or automotive environmental comfort. HVAC system design is a major sub discipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, and heat transfer.

Portable refrigeration air conditioners come in two forms, split and hose. These compressor-based refrigerant systems are air-cooled, meaning they use air to exchange heat, in the same way as a car or typical household air conditioner.

Split air conditioners have a split design with an external or out door unit that houses the compressor and one or more internal units that are served by the compressor and house the air handlers. This design makes them similar to central air conditioning units however the fact that they use smaller air ducts makes them less expensive and easier to install.

Central air conditioner systems are often installed in modern residences, offices, and public buildings, but are difficult to retrofit (install in a building that was not designed to receive it) because of the bulky air ducts required. A duct system must be carefully maintained to prevent the growth of pathogenic bacteria in the ducts.