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ABSTRACT
Smoke inhalation is the leading cause of death during structural fires. In order to improve life safety during a fire, smoke must be managed and kept away from building occupants. In high-rise buildings, the problem of smoke movement is compounded by a strong stack effect that draws smoke into the vertical shafts within the building and contaminates the fire-escape stairwells as well as the elevator shafts. If the smoke can be managed so that the stack effect can be used to advantage and egress routes can be maintained smoke free, then occupants will have a greater opportunity to avoid the effects of the smoke generated by the fie.
This paper investigates a smoke control strategy that involves using the elevator shafts as a route of smoke extraction coupled with pressurizing the stairwells with sufficient fresh air to maintain smoke-free conditions in the fire escapes for the entire height of the building. The practicality and efficacy of this smoke management strategy is evaluated by employing a differential-network smoke management computer program that simulates the paths that smoke will take during a simulated fire. The computer program is verified by comparing its results with a computational fluid dynamics (CFD) software tool, Fire Dynamics Simulator, for a simple building geometry. Both programs compare well when a reasonable set of discharge coefficients is used to calculate the gas flows through various openings in the modeled building. The differential-network model quantifies the paths that the smoke will take and determines the smoke properties with a significant reduction of computational time when compared to the time required to provide the CFD simulations.
Smoke generated by the fire will naturally tend to gravitate toward the elevator shafts, which exist at the lowest pressure within the building. Computer results show that large quantities of smoke can be directed away from occupants by controlling and exhausting the smoke through the top vent of the elevator shaft. If exhaust fans are used for smoke venting at the top of the elevator shafts and pressurization fans are used to maintain smoke-free conditions in the stairwells, then a prudent fire safety plan will result. The program output is used to quantify the amount of elevator exhaust and stairwell pressurization that is necessary to achieve safe...