Kitchen exhaust smoke and ventilation design principles are: range hood pipe as short as possible, the length shall not exceed 1.5 meters, the national standard for the design of range hoods is 1.5 meters exhaust length as a condition for the determination of noise and air displacement data. The length of the pipe exceeds 1.5 meters after the noise exceeds the standard, the ability to exhaust smoke decreased.　　Flue can only be installed with an elbow, that is, the range hood exit from the vertical flue to the horizontal flue. Adding a right angle elbow is equal to lengthening the flue by 1 meter.　　The ventilation position is as high as possible, preferably ceiling-mounted, and the ducts are also as short as possible to minimize duct damping noise.　　Based on the above requirements can ensure that the range hood and exhaust fan work low noise (noise less than 55 decibels of the national standard); ventilation effect to achieve the design capacity.