Pneumatic ventilation butterfly valves are non-sealing rotary butterfly valves used in ventilation ducts. They are designed and manufactured with a centerline disc plate welded to a short structural steel plate, serving as flow regulators or on/off controllers for gas media. Featuring low flow resistance, high flow coefficient, lightweight construction, and rapid actuation, this valve achieves proportional regulation when paired with a positioner. It is particularly suited for controlling large-diameter, high-flow flue gas in boilers and kilns.