RSET/ASET, a flawed concept for fire safety assessment

Abstract

SUMMARYFor the evaluation of occupant safety in the case of building fires, the Required Safe Egress Time/Available Safe Egress Time (RSET/ASET) concept has become widespread and is now commonly used in the fire safety engineering profession. It has also become commonly used by smoke detector (smoke alarm) manufacturers in assessing whether a particular detector technology is adequate. It is shown in this paper that the concept is intrinsically flawed and its use promotes the diminishment of fire safety available to building occupants. The concept innately ignores the wide variations in capabilities and physical condition of persons involved in fire. It is based on implicitly assuming that, after a brief period where they assess the situation and mobilize themselves, occupants will proceed to the best exit in a robotic manner. This assumption completely fails to recognize that there are very few fires, especially in residential occupancies, where occupants perished or were seriously injured who had endeavored to exit in this robotic manner. Instead, in the vast majority of fire death and serious injury cases, the occupants did not move in such a manner and their evacuation took longer than anticipated on the basis of robotic movement. There is a wide variety of reasons for this, and these are well known in the profession. The concept also ignores that there can be a wide variation in fire scenarios. The same building and the same fire protection features can be evaluated, but both RSET and ASET can change drastically, depending on the scenario used. The consequence of using the RSET/ASET concept for fire safety engineering or product design purposes is that fire deaths and injuries are permitted to occur, which are preventable.

An Arbitrary Polynomial Chaos-Based Approach to Analyzing the Impacts of Design Parameters on Evacuation Time under Uncertainty

“…The base case evacuation time is calculated from the 4 th degree expansions of T e constructed repeatedly for different values of exit width, whose uncertain parameters are taken as deterministic average values. The limitations of the RSET/ASET approach are widely known [25]. ASET may vary from 60-90 s in ultra-fast fire to 6-9 min in moderately fast growing fire [25].…”

“…The limitations of the RSET/ASET approach are widely known [25]. ASET may vary from 60-90 s in ultra-fast fire to 6-9 min in moderately fast growing fire [25]. The proper ASET value shall be the object of study considering the characteristics of each building, as a function of the inflammable material amount, type and distribution.…”

The philosophy of fire safety engineering in the shaping of civil engineering development

“…In an engineering practice, the most common use of evacuation modelling is through the available and required safe egress time concepts (ASET, RSET) [65]. These concepts play a key role in the quantification of the level of safety in a building.…”

Agent-Based Fire Evacuation Model as a Tool for Fire Safety Design Assessment in Malaysia

“…One of the important life safety parameters that can be quantified from those tools is the estimation of safe egress time, e.g. Available Safety Egress Time (ASET) and Required Safety Egress Time (RSET) (Babrauskas et al, 2010;Fleischmann, 2009). ASET is the time from fire ignition to the time at which tenability criteria are exceeded.…”