A pneumatic system is similar to a hydraulic system. However, instead of pressurized fluid in a hydraulic system, a pneumatic system employs pressured gas to affect mechanical motion. Pneumatic systems are extensively used in industry, where factories are commonly plumbed with compressed air or other compressed inert gases.
Pneumatically controlled valves are valves that are controlled by pressurized air. These may include liquid flow valves that are controlled by compressed air. Pneumatically controlling valves are valves that control the flow of pressurized air. Another medium such as water (hydraulics) or electricity, for example, may be used to control the valves.