Pneumatic cylinders are mechanical devices which use the power of compressed air to produce a force in a reciprocating linear motion.
Pneumatic cylinders use the stored potential energy of compressed air, and convert it into kinetic energy as the air expands in an attempt to reach atmospheric pressure. This air expansion forces a piston to move in the desired direction. The piston is a disc or cylinder, and the piston rod transfers the force it develops to the object to be moved.
Engineers prefer to use pneumatics sometime because they are quieter, cleaner, and do not require large amounts or space for fluid storage when compared to hydraulic cylinders.
Because the operating fluid is compressed air, leakage from a pneumatic cylinder will not drip out and contaminate the surroundings, making pneumatics more desirable where cleanliness is a requirement.