Air Conditioning is a method of providing clean air to an area at the proper temperarure and humidity. The term usually describes a refrigeration system designed to cool the air within a space. In the process of removing heat, the system also removes moisture from the air, further increasing comfort levels. Auxiliary filters may remove pollen, dust and other such pollutants from the air. Entire buildings are designed so that air temperature, humidity, and freshness are controlled by a single, central air conditioner. There are many different types of air conditioner, and of all these types people in the UK are mostly familiar with the type known as a "split system". This is an indoor fan coil unit connected via pipework to an outdoor condensing system.

The key element of the air conditioner is the refrigerant, most often a fluorocarbon that flows constantly through the conditioners mechanisms. Becoming a liquid and giving off heat when it is compressed, and becoming a gas and absorbing heat when that pressure is removed. The mechanisms that evaporate and compress the refrigerant are divided into two areas, an indoor air filter fan and cooling coil. And outdoor comprising of a compressor, condensor coil and fan.

In the air cooling cycle, warm humid air is drawn from the room through the filter and over the cooling coil. This coil contains a refrigerant fluid with a very low boiling point, i.e. it will have evaporated at room temperature. The warm air gives up its heat to the refrigerant and in the process, causes the refrigerant to vaporize. Cooled dehumidified air is blown back into the room. The vaporized refrigerant moves to the compressor, which pumps it under pressure to the condenser coils.

Here its heat is transferred by fan to the outside, and it is returned to the cooling coil as a liquid. Electric motors drive the compressor, blower and fan. A thermostat controls the compressor motor, turning it off when the room temperature reaches the desired level and restarting it as the room heats up.