Composite fireproof air duct: inner layer δ=1mm thick galvanized steel plate air duct, outsourcing 30mm thick rock wool board, outer layer δ=1mm thick galvanized steel plate air duct <br>(fire resistance rating not less than 1.0h)
Composite fireproof air duct: inner layer δ= 1mm thick galvanized steel sheet air duct, wrapped with 30mm thick rock wool board, outer layer δ= 1mm thick galvanized steel sheet air duct<br>(fire endurance not less than 1.0h)
Composite fireproof air duct: the inner layer δ=1mm thick galvanized steel duct, the outer layer δ=1mm thick galvanized steel duct wrapped with 30mm thick rock wool board. (Fire resistance limit not less than 1.0h)