BBS composite HVAC duct with 20mm thick weigh 1.6-1.9kg/m2 including PVC and aluminmum accessories. That means, the weight is only seventh or eighth of that of traditional galvanized steel broads per unit area. The employment of HVAC duct means the reducement of dead loads of building structure and the lower cost of construction. BBS composite HVAC duct have passed the sample tests by the Building Fire Protection Material Quality Surveillance and Examination Center of P.R of China and the fire rating meets the standard: GB-1997 of P.R of China, B1 level (self-extinguishing). The ducts totally reach the requirements of the specifications of fire rating of the material HVAC duct regulated by P.R of China. Both of the external and internal sides are embossed aluminum foils with 0.08mm thick. The outside of aluminum foil is covered with OP coating which greatly improve the corrosion resistance ability of BBS composite HVAC ducts. Comparing the results of salt mist tests between the aluminum foil with OP coating and the one without OP coating, the foil without coating takes on white staining in two hours in the peroxyacetic acid solution of 12% concentration, while the foil with OP coating does not have any white staining until six hours later. In the same way using caustic soda solution instead of peroxyacetic acid solution, there are lots of bubbles on the surface of the aluminum foil without coating just twenty seconds later. On the contrary, the one with OP coating have bubbles after forty-seven minutes. BBS composite HVAC duct is highly efficient in installment and assembly. Only simple manual instruments are enough for the whole process. Moreover, the ducts are easy-alternated. Each person can install 20m2 per day, which is four or five times of the capacity of produce and installment of traditional galvanized steel duct.