Air exhaust duct with valve for preventing smoke-back

The utility model relates to an air exhaust duct for preventing back smoke and back smell, which comprises a main air duct, an air exhaust pipe and a check valve, wherein a perforating hole is arranged on the wall of the main air duct, and the air exhaust pipe is arranged in the hole; the check valve is arranged in the air exhaust pipe and comprises a valve sheet and a valve sheet shaft, the valve sheet shaft is arranged on the upper part of the horizontal straight line of the valve sheet, and both ends of the valve sheet are fixed with the air exhaust pipe; the inner wall of the air exhaust pipe is provided with a convex separating and blocking sheet. Because the utility model uses a structure that the check valve is slantwise arranged in the air exhaust pipe, and meanwhile, because an air outlet of the air exhaust pipe 2 correspondingly uses the slantwise design, the ability for preventing the back smoke and the back smell is obviously improved. Additionally, because the utility model is provided with the check valve in the air exhaust pipe, the utility model has the advantages of simple structure and easy production, installation and maintenance.