Air conditioning engineers broadly divide air conditioning applications into comfort and process.

Comfort applications aim to provide a building indoor environment that remains relatively constant in a range preferred by humans despite changes in external weather conditions or in internal heat loads. Air conditioning makes deep plan buildings feasible, for otherwise they'd have to be built narrower or with light wells so that inner spaces receive sufficient outdoor air via natural ventilation. Air conditioning also allows buildings to be taller since wind speed increases significantly with altitude making natural ventilation impractical for very tall buildings. Comfort applications for various building types are quite different and may be categorized as,

Low-Rise Residential buildings, including single family houses, duplexes, and small apartment buildings

High-Rise Residential buildings, such as tall dormitories and apartment blocks

Commercial buildings, which are built for commerce, including offices, malls, shopping centers, restaurants, etc

Institutional buildings, which includes hospitals, governmental, academic, and so on

Industrial spaces where thermal comfort of workers is desired

In addition to buildings, air conditioning can be used for many types of transportation - motor-cars and other land vehicles, trains, ships, aircraft, and spacecraft.

Process applications aim to provide a suitable environment for a process being carried out, regardless of internal heat and humidity 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 these:

Hospital operating theatres, in which air is filtered to high levels to reduce infection risk and the humidity controlled to limit patient dehydration. Although temperatures are often in the comfort range, some specialist procedures such as open heart surgery require low temperatures (about 18 °C, 64 °F) and others such as neonatal relatively high temperatures (about 28 °C, 82 °F).

Clean rooms for the production of integrated circuits, pharmaceuticals, and the like, in which very high levels of air cleanliness and control of temperature and humidity are required for the success of the process.

Facilities for breeding laboratory animals. Since many animals normally only reproduce in spring, holding them in rooms at which conditions mirror spring all year can cause them to reproduce year-round.

Aircraft air conditioning. Although nominally aimed at providing comfort for passengers and cooling of equipment, aircraft air conditioning presents a special challenge because of the changing density associated with changes in altitude, humidity and temperature of the outside air

Data Centers Textile factors Physical testing facilities Plants and farm growing areas Mines Industrial Environments Food cooking and processing areas In both comfort and process applications, the objective may be to not only control temperature, but also humidity, air quality and air movement from space to space.