Explains the physical concepts of the steady fire, unsteady fire, zone fire model and the fire plume, which form the basis of atrium smoke management. States the approach to smoke control design calculation in codes in based on the zone fire model concept. In the zone model, smoke forms an upward-flowing fire plume that reaches the ceiling and is considered to form, a perfectly mixed layer under the ceiling of the room of fire origin. Shows that the commonly used virtual origin correction to the plume equations is not needed for atria smoke management. States that for the purposes of smoke management, the deviations of fire plume mass flows due to omitting the virtual origin correction can be neglected.

Units: Dual

KEYWORDS: year 1997, Atria, smoke, air flow, calculating, fire