The Colin Bay combination air handling unit can provide multiple functional section combinations according to customer requirements. All metals inside the unit are isolated from external metals through high-pressure polyurethane foam and specially designed rubber sealing strips. At the same time, the profiles and inner and outer panels are also formed as a whole through high-density polyurethane foam. The unit is flat, firm, and has good corrosion resistance, high temperature resistance, and salt water resistance; The bottom panel can withstand the weight of personnel, and the panels are coordinated with mortise and tenon double columns. The box has a double frame structure with ultra-high strength, ultra-low air leakage, no cold bridge, and can also avoid deformation of the unit during transportation and operation.