Air conditioning systems refer to the machines that make it possible to maintain the temperature of a closed room even in very hot surroundings. In tropical countries, this is essential as computers and other electronic gadgets are sensitive to temperature. The computers could overheat as the inside of the processors are already very hot from what it is doing. With air conditioning, temperatures are maintained at a comfortable level, dehumidify the air, and also filter the air inside the room.

A number of manufacturing processes, such as those used in the production of paper, textiles, and printed matter, require air conditioning for the control of conditions during manufacture. Air conditioning of this kind usually is based on adjusting the humidity of the circulated air. When dry air is required, it is usually dehumidified by cooling or by dehydration. In the latter process it is passed through chambers containing adsorptive chemicals such as silica gel. Air is humidified by circulation through water baths or sprays. When air must be completely free of dust, as is necessary in the manufacture of certain drugs and medical supplies, the air-conditioning system is designed to include some type of filter.