In order to save labor services and raw materials, the construction unit can calculate the spiral duct of each specification and model, and pay special attention to the length of other pipes, such as tee, electric air valve, elbow, etc., when dividing by the length of ventilation duct. There are many ways to install the spiral duct. When ordering, we must first decide which way to connect, and then decide to purchase. The connection methods are: looper flange method, socket method. When installing with looper flange method, the pipes of ventilation duct and spare parts should be the same size.