A series of full-scale experiments were carried out to investigate the smoke propagation behavior for t²-fires. The effect of corridor arrangement (size and smoke curtains) were analyzed. The corridor size and smoke curtains have beneficial effect to delay the smoke propagation to downstream corridors. In the experiments, quick mixing of smoke after the decay of fire was observed that result in blockage of corridors. In the prediction of smoke layer by using zone models, this effect is not taken into account. Thus there is a need to revise zone type equations to include smoke-air mixing during post decay period.