Mechanism activated, controlled, or powered by air or gas pressure. In comparison, hydraulic devices employ liquid pressure. See also pneumatics.

Pneumatic systems are similar to hydraulics in function, but hydraulic systems use liquid to power movement and work instead of gas. Pneumatic systems are simpler to design and simpler to manage than hydraulic systems, but hydraulic systems are capable of greater pressures: up to 10,000 PSI (pounds per square inch) with hydraulics, compared to about 100 PSI with pneumatics