Pneumatics is a branch of engineering that makes use of gas or pressurized air.
Pneumatic (compressed-air) fireless locomotives like this were often used to haul trains in mines, where steam engines posed a risk of explosion. This one is preserved H.K. Porter, Inc. No. 3290 of 1923.
A pneumatic butterfly valve
Compressed air is air kept under a pressure that is greater than atmospheric pressure.
Compressed air in vehicle tyres and shock absorbers is commonly used for improved traction and reduced vibration. Compressed air is an important medium for transfer of energy in industrial processes, and is used for power tools such as air hammers, drills, wrenches, and others, as well as to atomize paint, to operate air cylinders for automation, and can also be used to propel vehicles. Brakes applied by compressed air made large railway trains safer and more efficient to operate. Compressed air brakes are also found on large highway vehicles.
Air compressor station in a power plant
Technical Illustration of portable single-stage air compressor
Two-stage air compressor assembled on a horizontal tank and equipped with a Joule-Thomson (JT) type refrigerated compressed air dryer