Smoke and air plug valve is a type of plug valve specifically designed for flue systems. As it is used in smoke and air pipelines, the pressure is usually very low, so the steel plates used to make the plug valve are relatively thin. Therefore, it has the advantages of light weight and low production cost. Smoke and air plug valves are also divided into square flue plug valves and circular flue plug valves according to the shape of the pipeline. The large diameter can reach DN2800, and there are two types of materials: carbon steel and stainless steel.