Ten meters per second. Baidu question bank shows that after the positive pressure fan is started, the air pressure in stairwells, forerooms and walkways shows a downward trend, the air pressure in smoke-proof stairwells is 40 ~ 50pa, and the air pressure in forerooms, shared forerooms, fire elevator forerooms and closed doors (rooms) is 25 ~ 30pa. After the exhaust fan is started, the wind speed at the exhaust port should be 3 to 4 meters per second, but not more than 10 meters per second.