When the specification stipulates that the metal air duct is used, it should not be greater than 21m/s, and the wind speed of the smoke outlet should not be greater than 11m/s..

wind speed = exhaust air volume/exhaust area

suggestion: metal duct 15-21 exhaust 6-8

know the air volume, wind speed, static pressure and cross-sectional area, and calculate the length and height of the air duct. If the cross-sectional area is the cross-sectional area of the pipeline, then just calculate the friction resistance per meter of the pipeline. When the fan pressure is greater than 11% of the cumulative friction resistance of the total length of the pipeline, it is the longest value of the pipeline.

The correlation is as follows

The wind speed of mechanical forced air supply and mechanical smoke exhaust shall meet the following requirements:

1. When using metal air duct, it shall not be greater than 21m/s

2. When using nonmetallic material air duct such as concrete with smooth inner surface, it shall not be greater than 15m/s

3. The wind speed of air supply outlet shall not be greater than 7m/s; The wind speed of the smoke outlet should not be more than 11m/s

Natural smoke extraction is to exhaust or dilute the concentration of smoke by using the external windows, balconies, recessed corridors or special smoke outlets and shafts of buildings. In high-rise buildings, except for a class of public buildings with a building height of more than 51m and residential buildings with a building height of more than 111m, the smoke-proof stairwell and its antechamber near the external wall, the antechamber of the fire elevator and the shared antechamber should adopt natural smoke exhaust.