建筑火灾排烟系统设计中,有关排烟启动时间至今仍没形成统一的设计方法或分析方法,目前主要依靠专家经验或者依据排烟系统产品的性能进行取值和校验,存在很大主观性。该文通过综合考虑建筑火灾发展各阶段的经验模型,给出了计算烟气层高度的递推求解式,在此基础上利用灵敏度分析方法揭示了排烟启动时间对烟气控制效果的影响,提出了启动时间取值的最优区间、风险区间和失效界点。该研究有助于提高火灾排烟系统的设计合理性和安全性。 Building fire exhaust system design, the start time of the smoke has not yet formed a unified design methods or analysis methods, the current mainly rely on the experience of experts or based on the performance of smoke exhaust system values ​​and checks, there is a great subjectivity . Based on the empirical model of various stages of building fire development, this paper presents a recursive formula to calculate the height of flue gas layer. On this basis, the sensitivity analysis method is used to reveal the influence of flue gas start-up time on the flue gas control effect. The optimal interval of starting time, risk interval and failure threshold are proposed. This study helps to improve the design rationality and safety of the fire exhaust system.