RSET/ASET, a flawed concept for fire safety assessment

Fire and Materials (Impact Factor: 1.32). 11/2010; 34(7):341 - 355. DOI: 10.1002/fam.1025


For 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. Copyright © 2010 John Wiley & Sons, Ltd.

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Available from: Vytenis Babrauskas, Dec 17, 2013

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Article: RSET/ASET, a flawed concept for fire safety assessment

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    • "Limitations Babrauskas (2009 [14] "
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    ABSTRACT: The basic concept in the assessment of occupant safety in a building under fire conditions is the determination of the time when occupants are able to safely escape before hazardous conditions sets in. The Available Safe Egress Time/Required Safe Egress Time (ASET/RSET) concept of fire safety assessment in performance based fire safety engineering design has become widely used amongst fire safety engineering practitioners, since its inception more than thirty years ago. However, the adequacy of this approach has only been occasionally deliberated on and not well addressed in detail. Discussions were usually focused on the weaknesses and inadequacies in the assumptions and methodologies which impact upon the outcome of the ASET and RSET parameters, rather than on the ASET/RSET concept itself. The original ASET/RSET approach was derived from a simple two-zone model for a single compartment by Cooper in 1980, but is still being applied to larger and more complex buildings today. This is despite the advancement of sophisticated three- dimensional simulation models producing highly detailed results, whereby the smoke layer is no longer uniform and the extent of the area of untenable conditions is a transient state and may develop only over a portion of the compartment area. The continued application of the ASET/RSET approach in these circumstances may lead to varied interpretation of the egress terms, leading to departures from the intended purpose and scope of providing the basic measure of assessing egress safety that was originally devised by Cooper. There is also little published literature available on viable alternatives to this simplified means of assessing safe egress from fire that was originally derived from a zone model concept. This paper provides a brief review of the ASET RSET methodology, and introduces an alternative means of fire safety assessment based on the utility of a given space over time. The alternative scheme enables a dynamic approach to assessing the level of safety that is more appropriate for use with advanced simulation models providing transient three-dimensional environments in more complex building layouts.
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    • "An immediate action is to implement appropriate fire safety management by assigning more security guards to those places with extended travel distance to avoid any small accidental fire from happening. Big halls for public transport and tunnels going through FEA/PBD with timeline analysis should be checked carefully [17] [18] [21] [22]. Of course, full-scale burning tests must be carried out to avoid using flawed concept [20] "
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