When the length of horizontally suspended main and dry galvanized flat ducts exceeds 20m, fixing points to prevent swinging should be set up, and there should not be less than 1 for each system. The screw holes of the hanger should be machined. Hanger rods should be straight, with complete and smooth threads. After installation, the force of each sub-branch and hanger should be uniform without obvious deformation. Adjustable vibration isolation support and hanger for galvanized sheet air duct or air-conditioning equipment should be adjusted according to the requirements of the design in terms of tension or compression. The hoop bracket, the folded corners should be straight, the hoop should be close to and tighten the galvanized sheet air duct. Installed in the bracket of the round galvanized sheet metal duct should be set up to support and hoop, its arc should be uniform, and with the galvanized sheet metal duct outside diameter. Inspection number: 10% by number, not less than 1 system. Inspection method: measuring, observation and inspection.