Abstract: In this paper through analyzing smoke-flow field theoretically, it is discussed that the effect of air flow in a high-rise building is as a result of gas expansion by the temperature, the chimney effect, the outdoor wind power and a ventilation and air conditioning system when firing. The flow field at the staircase door is theoretically found. The way in which the diffusion of smoke is controlled is advanced according to the principle of flow line-rate of flow and based on the previous experimental researches by others, the mathematical mode of design parameter for the smoke preventing air curtain is inferred.

Key words: preventing-smoke, potential flow, air curtain, flow functions