An air compressor is a pneumatic device that converts power (from a motor, diesel, or gasoline engine, for example) into potential energy stored in pressurised air (i.e., compressed air). An air compressor increases the pressure of a storage tank by forcing more and more air into it using one of several methods. The air compressor turns off when the pressure in the tank reaches its engineered top limit. The compressed air is then stored in the tank until it is needed. The compressed air’s energy can be used for a variety of purposes by harnessing the air’s kinetic energy as it is released and the tank depressurizes.

When the tank pressure drops below a certain level, the air compressor kicks in and re-pressurizes the tank. An air compressor differs from a pump in that it works with any gas or air, whereas pumps function with liquids.