An air conditioner is an appliance, system, or mechanism designed to extract heat from an area using a refrigeration cycle. In construction, a complete system of heating, ventilation, and air conditioning is referred to as HVAC. Its purpose, in the home or in the car, is to provide comfort during hot days and nights.

Air conditioning applications:
- Comfort applications aim to provide an indoor environment that remains relatively constant in a range preferred by humans despite changes in external weather conditions or in internal heat loads.
** for various building types is quite different and may be categorized as:
* Residential Buildings including single family houses and hi-rise buildings.
* Institutional Buildings includes Hi-Rise offices, large complex buildings, hospitals, and so on.
* Commercial Buildings which are built for profit and commerce, including malls, shopping centers, apartment housings, etc.

- Process applications aim to provide a suitable environment for a process being carried out, regardless of internal heat loads and external weather conditions. Although often in the comfort range, it is the needs of the process that determine conditions, not human preference.
**Process applications include:
* Hospital operating rooms
* Cleanrooms
* Facilities for breeding laboratory animals.
* ircraft air conditioning.
* Data Processing Centers
* Textile Factories
* Physical Testing Facilities
* Plants and Farm Growing Areas
* Nuclear Facilities
* Mines
* Industrial Environments
* Food Cooking and Processing Areas

Air conditioning system equipment
*Evaporation coolers
*Absorptive chillers
*Central air conditioning