pneumatic device, any of various tools and instruments that generate and utilize compressed air. Examples include rock drills, pavement breakers, riveters, forging presses, paint sprayers, blast cleaners, and atomizers. Compressed-air power is flexible, economic, and safe. An air device creates no spark hazard in an explosive atmosphere and can be used under wet conditions without electric-shock hazard.
The ordinary hand bellows, used by early smelters and blacksmiths for working iron and other metals, was a simple type of air compressor. The air intake consisted of several holes in a piece of wood, covered with flaps that served as valves. A simple check valve in the discharge prevented air from being drawn back into the bellows during the suction stroke. In the time of Hero (probably 1st century AD), a simple jet-type compressor was used to provide air for smelting and forging.
