The Movement of Smoke in Horizontal Passage under the Soffit against an Air Flow

A system to control smoke flow at fIre by providing differential pressure between rooms has frequently been adapted to many buildings. The pressurized smoke control system of a vestibule at stairwell is one of the examples. Supposing the initial stage of fIre, this study is to grasp the relationship between the air velocity to prevent the smoke flow in a horizontal passage with the soffIts and the properties of smoke (smoke layer temperature, smoke layer thickness and buoyancy) near the soffIt. It was concluded that the air velocity under the soffIt v and ( ..6 pi p )In, and v and ( L\ QfI')'n are in proportional relationship respectively.