Air conditioning (often referred to as
A/C or
AC) is the process of altering the properties of
air (primarily
temperature and
humidity) to more comfortable conditions, typically with the aim of distributing the conditioned air to an occupied space such as a building or a vehicle to improve
thermal comfort and
indoor air quality. In common use, an
air conditioner is a device that lowers the air temperature. The
cooling is typically achieved through a
refrigeration cycle, but sometimes
evaporation or
free cooling is used. Air conditioning systems can also be made based on desiccants.