Air compressors are used to compress air. Air that is under pressure contains energy that can be used to power machines and tools. The first industrial use of compressed air was to provide power for drills.
There are a variety of types of air compressors. Generally, compressors are either dynamic compressors or positive displacement compressors. Dynamic compressors use vanes or impellers to compress the fluid. Positive displacement compressors depend on the compression of their surroundings, and are available in two types: reciprocating and totalling.
Two-stage air compressors run cooler than single-stage air compressors. As air is compressed, its temperature rises, so the air is cooled as it moves between stages through a process called intercooling. This is carried out by an air-cooled or water-cooled heat exchanger. When the heat exchanger removes all of the extra heat generated by the compression, it is a perfect intercooler.
Compact compressors don't include an air storage tank. They run continuously, and are capable of generating lower pressures than other compressors. They are generally inexpensive, and aimed at home use
Compressors are available in industrial-grade and in models for the home. The home models are generally smaller and cheaper, with the idea that you won't sit at home and run your compressor nearly as often as if you were using it at work. Industrial compressors generally have higher PSI ratings and can run for longer periods of time.
Tools powered by compressed air include: nail guns, air hammers, cutters, drills, wrenches, sandblasters, grease guns, spray guns and welders.