Kitchen exhaust system design method: kitchen exhaust 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. The flue can only be installed with an elbow, that is, the range hood outlet by vertical.