Abstract: A series of mechanical smoke exhaust experiments were conducted in a bench-scale long channel. Two opening conditions were simulated, two ends being opened and a single end being opened respectively. The influence of the turbulent entrainment intensity at the smoke layer interface, due to different relative locations of exhaust openings to fire source, on the mechanical smoke exhaust efficiency is studied. The results show that when the exhaust openings are operated in the stage of one-dimensional horizontal spread, the turbulent entrainment effect at the smoke layer interface would be evidently intensive, leading to a poor smoke control effect. It is recommended to operate the exhaust openings in the range of the longitudinal distance to fire source less than 1.33 times of the channel width. And for the channel with one end closed, additionally exhaust openings should be opened near the closed end.