What is the definition of a pneumatic thermostat? A pneumatic thermostat is a device that controls the temperature of an environment or material by controlling the flow of air or other gases. It works by sensing the temperature of the environment or material and then adjusting the flow of air or gas accordingly. The thermostat is made up of a sensing element, a control unit, and a valve. The sensing element is used to detect the temperature of the environment or material, which is then sent to the control unit. The control unit then adjusts the valve to control the flow of air or gas. This helps regulate the temperature of the environment or material. Pneumatic thermostats are often used in controlled environment rooms, industrial processes, and many other applications. They are reliable, efficient and cost-effective, making them a popular choice for controlling temperature.