Accurate determination of critical safety height during available safe egress time assessment

When evaluating the ASET (available safe egress time), the fire scenario and the heat release rate (HRR) of the fire need to be set firstly according to the function and the combustible materials of the building, then CFD (Computational Fluent Dynamics) software is used to perform simulations. The ASET is obtained at the time when the hazard index of smoke reaches the minimum value at a safety height, and this height could be defined as critical safety height. It is very important to select critical safety height and heat release rate for the accuracy of the simulation results. The variation of selection of the critical safety height in references is large and it is lacking of credible evidence. This paper discusses the critical safety height based on statistics, probability and ergonomicsvvso as to improve the accuracy, credibility and reliability of the numerical simulation.