The paper is aimed to study the factors affecting the smoke movement

and obtain the experimental data on the smoke spread in the semi-horizontal extraction system in tunnel fires.A series of tests are conducted in a model tunnel of ratio 1:10

and the theoretical analysis of smoke flow at the exhaust in-lets and duct is performed.The results indicate that the theoretical analysis is basically consistent with the model test data.Smoke is hot at the near field of the fire since little cold air is drawn to the fire and the mixing of smoke and air is not strong.However

the smoke temperature near the exhaust inlets far away from the fire is low

because of the heat loss to the boundaries and more mixing with cold air.Performance of the extraction of semi-horizontal system in tunnel fire is dependent on number

spacing

area of exhaust inlets and distance from the fan.