Duct pipes are equipment for ventilating locations such as factories or stores. Their important role is to discharge bad air that has accumulated indoors to the outside and bring in the fresh air. They are usually made from zinc-plated iron plates, but depending on the installation environment, heat-resistant Galvalume steel plates, rust-resistant stainless steel, or corrosion-resistant and chemical-resistant PVC coated steel plates may be used. Two differently shaped types are available, square ducts and round ducts. These can be freely installed by combining straight pipes and elbows according to conditions at the worksite. Strong and highly concentric spiral pipes are used as the standard for the straight pipes of round ducts. Compared to square ducts, round ducts have much lower friction loss and leakage, enabling their use as high speed, dust collection and smoke exhaust ducts. Three branch pipe types are available from 45°C to 90°C that varies according to the angle size: T pipes with an angle 90 degrees from the trunk, Y pipes with an angle 45 degrees from the trunk, and TY pipes with an angle 45 to 90 degrees from the trunk.