Airconditioning

Air conditioning refers to the process of treating air to control its temperature, humidity, cleanliness, and distribution to improve comfort or meet process requirements in built environments and vehicles. Modern systems typically comprise an indoor unit or space, an outdoor unit, a circulating air pathway, and a refrigerant that cycles between components.

The development of air conditioning began in the early 20th century. Willis Haviland Carrier designed the first modern system in 1902 for a printing plant, intended to stabilize humidity and temperature. The technology evolved into central systems for buildings, packaged units for commercial spaces, and compact appliances for homes and vehicles.

Most air conditioning operates by a closed refrigeration cycle. A refrigerant absorbs heat from indoor air in an evaporator coil at low pressure, then is compressed to high pressure and temperature, releasing heat to outdoors in a condenser coil. An expansion device lowers the refrigerant pressure, continuing the cycle. In addition to cooling, many systems dehumidify by removing moisture from the air and thereby affecting perceived comfort.

Types include central air systems that use ducts; split systems with separate indoor and outdoor components; packaged units that place all components outside or in a roof; and ductless or mini-split systems. Portable and window units offer localized cooling.

Efficiency is commonly described by metrics such as SEER (Seasonal Energy Efficiency Ratio) or EER. Refrigerants have environmental implications, with regulatory phaseouts of older substances and shifts toward lower global warming potential options. Regular maintenance, including filter replacement and coil cleaning, is essential for performance and safety.