The main function of an air compressor is to change free air into high pressure air. This high pressure air can be used for various purposes, such as operating power tools, pneumatic tools (which operate with air pressure), painting, cleaning surfaces, filling tires, and much more. Air compressors are used in various industries, such as automotive to operate pneumatic tools such as air guns, in the construction industry to drive nails or use air drills, in painting, in chemical manufacturing, and in many other applications.