人员疏散准备时间及其对火灾风险评估结果的影响

火灾时人员的有效避难评估是火灾风险评估中的重要组成部分.作为人员疏散时间中重要组成部分的疏散准备时间服从概率分布,而通常计算中往往将其简单取为常数.将人员疏散准备时间简单取为常数时,有可能产生模拟计算结果比实际偏差大、疏散情形与真实情况不符的情况.以一座办公建筑为例进行了计算,将人员疏散准备时间简单取为常数时与人员疏散时间服从正态分布的情况进行了比较,并分析了对火灾风险评估结果的影响.

Pre-evacuation time for occupants and its effect on fire risk assessment

The present paper aims to introduce the authors' study on the pre-evacuation time for the occupants and its effect on the fire risk assessment. As is known, a very important safety criterion is to ensure the safety for the occupants to evacuate from the building before the onset of a potential hazard. For the time being, it is generally agreed that the required safe egress time (RSET) is less than or equal to the available safe egress time (ASET). As an important factor of RSET, the occupant pre-evacuation time should be restricted by psychological behaviors, the occupant age, the familiar degree of the occupants to the building, etc. For the RSET time line, emphasis should be placed on the length of their escaping time experienced by occupants from the building to a safer place through the escaping route. It naturally involves some kind of time lag, because, first of all, if the occupant pre-evacuation time can be taken as a constant, the evacuation process does not reflect the real evacuation time. The pre-evacuation time from different functional buildings is naturally different. For example, if occupants are widely distributed in multi-enclosure buildings, such as hotels or apartment blocks, the pre-evacuation time is likely to be of great variation. When the occupants are all together in a single enclosure, such as supermarkets or theatres, the range of pre-evacuation time tend to be similar. Moreover, there will be a deviation of occupant evacuation time when calculated with probability methods. Secondly, different means for evacuation can be used to compare the occupant evacuation time for normal distribution and the constant to be used. And, finally, underestimate of evacuation time are presented to analyze the effect on the fire risk assessment.