In sections where fire resistance is required, cable ladder racks or trays can be equipped with flame-retardant or flame-resistant materials such as boards and meshes to form a closed or semi-closed structure. Measures such as applying fire-retardant coatings to the surface of the bridge and its supporting brackets should be taken. The overall fire resistance of the structure should comply with national regulations or standards. The selection of width and height for槽式 cable trays should meet the requirements of fill ratio. Generally, the fill ratio for power cables in trays and ladders can be 40% to 50%, and for control cables, 50% to 70%. It is also advisable to reserve 10% to 25% for engineering development allowances.