RSET/ASET,a flawed concept for fire safety assessment

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.     

Effects of passenger blockage on smoke flow properties in longitudinally ventilated tunnel fires

This paper investigates the effects of passenger blockage on smoke flow properties in longitudinally ventilated tunnel fires. A series of numerical simulations were conducted in a 1/5 small-scale tunnel with the different heat release rates (50-100 kW), longitudinal ventilation velocities (0.5-1 m/s), passenger blockage lengths (2-6 m), and ratios (0.17-0.267). The typical smoke flow properties in different tunnel fire scenarios are analyzed, and the results show that under the same heat release rate and longitudinal ventilation velocity, the smoke back-layering length, maximum smoke temperature, and downstream smoke layer height decrease with increasing passenger blockage length or ratio. The Li correlations can well predict the smoke back-layering length and maximum smoke temperature in tunnel fire scenarios without the passenger blockage. When the passenger blockage exists, the modified local ventilation velocity that takes the blockage length and ratio into account has been proposed to correct the Li correlations. The smoke back-layering length and maximum smoke temperature with the different blockage lengths and ratios can be predicted by the modified correlations, which are shown to well reproduce the simulation results.     

Concepts for fire protection of passenger rail transportation vehicles: Past,present, and future

Recent advances in passenger rail transportation, fire test methods, and hazard analysis necessitate re-examination of requirements for fire safety. Several studies have indicated nearly random ability of current bench-scale tests to predicts actual fire behavior. Fire safety in any application, including transportation, requires a multi-faceted approach. The effects of vehicle design, material selection, detection and suppression systems, and emergency egress and their interaction, on the overall fire safety of the passenger trains must all be considered. The strengths and weakness of current methods for measuring the fire performance of rail transportation systems are evaluated. A systems approach to fire safety which address typical passenger train fire scenatios is analyzed. A rationale is presented for the direction in which most fire science-oriented organizations in the world are clearly headed – the use of fire hazard and fire risk assessment methods supported by measurement methods based on heat release rate.     

Engineering egress data considering pedestrians with reduced mobility

To quantify the evacuation process, evacuation practitioners use engineering egress data describing the occupant movement characteristics. These data are typically based to young and fit populations. However, the movement abilities of occupants who might be involved in evacuations are becoming more variable—with the building populations of today typically including increasing numbers of individuals: with impairments or who are otherwise elderly or generally less mobile. Thus, there will be an increasing proportion of building occupants with reduced ability to egress. For safe evacuation, there is therefore a need to provide valid engineering egress data considering pedestrians with disabilities. Gwynne and Boyce recently compiled a series of data sets related to the evacuation process to support practitioner activities in the chapter Engineering Data in the SFPE Handbook of Fire Protection Engineering. This paper supplements these data sets by providing information on and presenting data obtained from additional research related to the premovement and horizontal movement of participants with physical‐, cognitive‐, or age‐related disabilities. The aim is to provide an overview of currently available data sets related to, and key factors affecting the egress performance of, mixed ability populations which could be used to guide fire safety engineering decisions in the context of building design.     

特殊消防设计在大型高铁车站设计中的运用

近年来在基础设施建设的投入显著增强,出现了较多的超高层建筑和大体量单体建筑,这就在建筑消防设计方面带来了许多问题。以在建的大同至张家口客运专线某站为例,探讨特殊消防设计在大型单体建筑中的运用,提出了一些特殊消防设计方案,进行了一系列消防安全性验证,证明了特殊消防设计能够解决大型单体建筑消防设计与现行规范的矛盾。     

Design car fire size based on fire statistics and experimental data

Passenger vehicle fires present a significant fire hazard in enclosed car parks. Accordingly, this hazard is often used as a design fire scenario for the application of fire protection systems. Specific fire protection standards, like NFPA 88A:2019 and NFPA 502:2020 in the United States (US) or BS 7346-7:2013, NBN 21-208-2:2014, VDI 6019-1:2006, NEN 6098:2010 and ITB 493:2015 in Europe, provide varying requirements for car park fire protection. Car parks fire strategies, especially when smoke control systems are used, often make use of performance-based methods, in which fire growth (ie, heat release rate [HRR]) plays a fundamental role. The chosen HRR can influence the specification of car park construction and on smoke control system calculations. This article presents a review of 44 full-scale car fire tests together with Polish and British passenger car fire statistics from the last 8 years. Based on the collected data and the averaged tests, HRR values provided in this article could assist local authorities and stakeholders determine optimal fire safety design criteria for car parks.     

Validation of the lumped parameter code COCOSYS against large‐scale OECD PRISME 2 fire experiments

Fire safety analysis is a major issue for nuclear power plants (NPPs) in the context of deterministic safety assessments as well as of probabilistic safety analyses. Oil reservoirs and cables represent major fire loads. Therefore, simulations of oil and cable fires are of interest for quantifying the risk of such internal hazards in NPPs. To investigate the applicability of lumped parameter (LP) modelling, validations against fire experiments are required. In this way, results obtained with the LP code COCOSYS for simulations of oil and cable fire experiments conducted in the OECD PRISME 2 Project are presented. The PRISME 2 VSP (vertical smoke propagation) tests involving oil fires in a confined and mechanically ventilated facility were used to assess the ability of the LP code to simulate smoke propagation through a horizontal opening from the fire compartment to a compartment on top of it. As it was already identified in the “International Collaborative Fire Modelling Project (ICFMP),” this type of opening might cause problems in fire simulations, particularly for zone or LP fire models. In these simulations, attention has been paid to the coupling between the fire and the surrounding environment due to the decrease of oxygen concentration. Furthermore, different cable materials have been tested in the PRISME 2 CORE (completing and repeating) test campaign. By simulating the CFS‐3 (cable fire spreading) test with confined underventilated conditions, the applicability of the COCOSYS cable fire model with input parameters deduced from open atmosphere fire tests (CORE‐2) was analysed. Results show that the applicability of a LP fire model to predict the pyrolysis rate is partly limited for both oil and cable fires, in confined environment. However, simulations with prescribed pyrolysis rates show encouraging results in good agreement with the experimental data and underline the capability of the LP code COCOSYS to simulate the interaction between the thermal hydraulics inside compartments and the fire source.     

New approaches to determine the interface height of fire smoke based on a three-layer zone model and its verification in large confined space

Large confined space has high incidence of fires, which seriously threatens the safety of people working there. Understanding the distribution of smoke in such large space is critical to fire development prediction and smoke control. Three improved methods for the stratification interface prediction of fire smoke are developed, including of improved intra-variance, integral ratio and N-percentage methods. In these methods, the interface height is determined by the vertical temperature distribution based on a three-layer smoke zone model, which is an improvement of a two-layer zone model. Thereafter, the three improved methods are applied to several typical fire cases simulated CFD to predict the smoke interface, and their applicability and reliability are verified by comparison of the smoke stratification results with the filed simulation results. Results show that the three improved methods can effectively determine the location of the three-layer zone model's interface, and they have the ability to predict smoke interface for fires with different fire source types and ventilation conditions.     

市政道路下穿铁路立交桥雨水泵站设计探讨

市政道路下穿铁路时,需要重点考虑雨水排水问题。雨水泵站设计的合理性直接关系到市政道路运行的安全性和畅通性。结合淮南市中兴路下穿淮南铁路立交桥工程施工设计,对雨水泵站的选址、泵站规模确定、水泵选型等进行探讨,并提出合理化建议。     

CFD analysis of smoke backlayering dispersion in tunnel fires with longitudinal ventilation

In a longitudinally ventilated tunnel fire, the backlayering flow propagated in the opposite direction to the air current is the most fatal contaminations to users which are blocked upstream of the fire. In the present paper, numerical simulations were conducted using Fire Dynamic Simulator, which is based on large eddy simulations to estimate the backlayering arrival time in a longitudinally ventilated tunnel fire. The effect of a vehicle obstruction on the backlayering arrival time will be also investigated. For this, a vehicle model occupying about 31% of the tunnel cross section is simulated upstream of the fire source with its location relative to the tunnel floor is varied. The numerical investigation shows that the inertia and the buoyancy forces produced by ventilation and fire, respectively, affect the backlayering spread. The backlayering arrival time increases with the longitudinal ventilation velocity while it decreases with the fire heat release rate. When a vehicle obstruction existed within the tunnel, the numerical results show an increase of backlayering arrival time. This increase is significantly more important with the fire distance when the vehicle obstruction approaches the tunnel floor. Two correlations are developed, with and without obstruction in the tunnel, to predict the backlayering arrival time against the distance to fire. Copyright © 2016 John Wiley & Sons, Ltd.     

Studies on the Thermal Behavior of Polyurethanes

The number of fires appear to be increasing all over the world with some big fires started from burning sofa polyurethane foam (PUF). The general public is quite concerned about the risk of fire due to the extensive use of polyurethane-based materials. Better understanding of the fire behavior of the materials would provide guidelines on fire safety provision. The first step is to review the thermal decomposition mechanisms of polyurethane under different environmental conditions, which will be reported in this paper. Recent studies on the thermal decomposition kinetics and thermal stability of polyurethane are described. Thermal decomposition and combustion reactions of polyether-polyurethane and polyester-polyurethane in air and nitrogen atmospheres investigated by using thermogravimetry analysis will then be outlined. The kinetic processes of polyurethane decomposition studied by the model fitting method are discussed. Polyester-polyurethane was found to be thermally more stable than polyether-polyurethane. The presence of oxygen would significantly affect the breaking down of the polymeric chains. Fire retardants for polyurethane are also briefly reviewed. Results are useful for developing fire retardants for polyurethane-based materials with better fire behavior.     

Evacuation experiments in a virtual reality high‐rise building: exit choice and waiting time for evacuation elevators

The egress strategy in high‐rise buildings has traditionally been based on the sole use of stairs for evacuation. However, it is becoming more common to include evacuation elevators in the egress strategy in high‐rise buildings. Traditionally, evacuation elevators have not been allowed as an evacuation route, and people have been instructed to not use elevators in case of fire. This means that people might still not consider evacuation elevators even if they are designed to be safe in case of fire. Even if people choose evacuation elevators, they might not be willing to wait very long for an elevator to arrive. Virtual reality (VR) experiments were conducted to study exit choice and the waiting time for evacuation elevators in high‐rise buildings. The experiment was performed in a VR lab with a VR model of an existing high‐rise building. Results suggest that a simple way‐finding system using green flashing lights can influence people to more likely choose the elevator as their first evacuation choice. The results also show that the general trend is that people wait for either a limited time (<5 min) or a long time (>20 min). Copyright © 2015 John Wiley & Sons, Ltd.     

Experimental and numerical analysis of fire scenarios involving two mechanically ventilated compartments connected together with a horizontal vent

This work deals with an experimental and numerical investigation of a fire scenario involving two rooms mechanically ventilated and connected together with a horizontal vent. The objective is to improve the understanding of the physical phenomena and to assess the capability of computational fluid dynamics (CFD) numerical simulations to predict flow field for such a fire scenario. The study is based on a set of large‐scale fire experiments performed in the framework of the OECD PRISME‐2 project in the DIVA multi‐room facility of the Institut de Radioprotection et de Sûreté Nucléaire (IRSN) and of numerical simulations performed with the ISIS CFD code. The fire scenario consists of two rooms, one above the other, mechanically ventilated and connected to each other with a horizontal vent of 1 m². The fire is a heptane pool fire located in the lower room. The analysis focuses on the coupling between the burning rate, the flow at the vent, and the configuration of the mechanical ventilation. Several regimes of combustion are encountered from well‐ventilated steady fire to under‐ventilated unsteady and oscillatory fire. The results show that the burning rate is controlled by both the mechanical ventilation and the downward flow from the vent. The numerical simulations highlight the specific pattern of the oxygen concentration field induced by the downward flow at the vent.     

水电解制氢站工程设计中安全问题的探讨

为了最大程度避免水电解氢气站火灾、爆炸事故的发生,在现行水电解制氢站相关设计规范的基础上,提出了规范中未要求的三点工程设计安全措施,并对该类措施实施增加的投资成本与无对应安全措施所造成的事故成本进行了分析比较。在现有设计规范的基础上,通过该类安全措施使得水电解氢气站设计达到无安全隐患的指标,可最终实现安全生产的目的。     

Evaluation of the room smoke filling time for fire plumes: Influence of the room geometry

The article examines numerically and theoretically the effects of room aspect ratio on the fire smoke filling process. It aims to evaluate the two-zone models used in fire safety engineering to predict the smoke filling times. Using Fire Dynamics Simulator, numerical simulations are performed and compared to a simplified zone model. The results show that the two-zone model overestimates the smoke filling time in the case of a compartment with a large surface area. To improve the predictions of two-zone models, simple correlations are established for the duration of the phenomena occurring before the formation of a two-layer stratification in a fire compartment. These new correlations allow the zone model to be significantly improved.     

Numerical investigation of tube furnace toxicity measurement method (ISO 19700)

ISO TS 19700 describes a test method for the generation of fire effluent and the identification and measurement of its constituent combustion products. The method has been previously accepted as a British Standard (BS 7990:2003) and as an IEC Standard (IEC 60695‐7‐50), which involves the decomposition of materials or products under various decomposing conditions occurring in different types and stages of real fires. It uses a moving test specimen and a tube furnace at different temperatures and air flow rates as the fire model. Simulations of flow and combustion conditions inside the tube (Purser) furnace were carried out and validated with the measurements. The objective of the present study is to demonstrate the validity of using computational fluid dynamics (CFD)‐based fire field modelling techniques to predict the fire environment inside the tube furnace. These numerical investigations are also used to verify critical experimental operating parameters that affect the performance of the tube furnace and understand the modus operandi of the tube furnace toxicity method. Copyright © 2011 John Wiley & Sons, Ltd.     

Predicting the thermal response of timber structures in natural fires using computational ‘heat of hydration’ principles

The thermo‐physical response of timber structures in fire is complex. For this reason, debate still exists today as to the best approaches for simulating thermal response in fire using tools such as finite element analysis (FEA) modelling. Much of the debate is concerned with the thermal properties of timber, for example, conductivity, specific heat and density, at elevated temperature and how such properties should be implemented or interpreted in numerical calculations. For practitioners intending to use modelling as a fire design tool for timber buildings, guidance exists on the thermal properties of softwood in Annex B of EN 1995‐1‐2. These properties are limited for use under standard fire exposure conditions because of the way in which they were derived from calibration against focussed test data. As a result, they cannot be applied to non‐standard fires, which are more representative of real fires due to a combination of varying heating rates and the decay phase of fire development. The limitations of the standard fire test (and associated curve) are widely understood. As a result, much recent structures in fire research has focussed on the ‘performance based design’ of buildings subject to increasingly realistic fire conditions. Such an approach allows engineers to quantify the level of safety that can be achieved in a building should a fire occur. In addition, the design of buildings to withstand fires proportionate to the risks foreseen and also the geometry present results in better value buildings that are inherently more robust. For the same approaches and associated benefits to be realised for timber buildings, then a number of barriers must be overcome. The most obvious of these is engineers' ability to determine timber structure temperatures as a result of fires other than the standard fire curve. This however presents a number of challenges. Upon heating, the moisture bound within begins to evaporate, volatiles begin to flow from the heated surface and char forms. The rate of which these behaviours occur and the nature of the char that forms depends on a number of factors, but most notably the rate of heating. Upon cooling, the timber member continues to generate heat energy as the surface oxidises. As a result, any models intended to simulate temperature development must consider the relationship not only between temperature and thermo‐physical characteristics but also between heating rate and the process of heat generation. Many models have been developed for this purpose; however, they are extremely complex and are some way from being ready for implementation as design tools. This paper proposes implementing ‘heat of hydration’ routines, intended for the curing of concrete structures, to simulate the heating and cooling process in timber structures. Such routines are available in many commercial FEA software packages. The adoption of the hydration routines allows the heat generation process, as a result of oxidation, to be considered in parallel with solid phase heat transfer using apparent thermal properties. The approach is shown to be very effective in simulating temperature development in timber members subject to parametric design fires. The models developed are benchmarked against experiments conducted in the 1990s by SP Trätek. Predictably, a number of the heat generation parameters adopted are shown to depend on the fire dynamics considered. However, recommended parameters are given that provide an acceptable level of accuracy for most design purposes. Copyright © 2012 John Wiley & Sons, Ltd.     

A correlation for predicting smoke layer temperature in a room adjacent to a room involved in a pre‐flashover fire

Advanced fire modelling software have been developed and improved during the last couple of decays and these kinds of software have been shown to be valuable tools for fire safety engineers. However, the advances made have not replaced the need for simple hand‐calculation methods. Simple hand‐calculations methods can be used to obtain a first estimate of, for example, smoke layer temperatures in a performance‐based design or to help an engineer determine if it is necessary to perform a detailed computational fluid dynamics calculation, but the current hand‐calculations methods are limited. The current methods can for example only predict smoke gas temperatures in the fire room. A correlation that could predict temperatures in an adjacent space would be useful in performance‐based design when, for example, evaluating the conditions for evacuees or sensitive equipment in an adjacent space to the room of fire origin. In this paper, a correlation for predicting gas temperatures in a room adjacent to a room involved in a pre‐flashover fire is developed. The correlation is derived from results from computer simulations and the external validity is studied by comparing results from the correlation with full‐scale test data. Copyright © 2012 John Wiley & Sons, Ltd.     

The influence of emergency signage on building evacuation behavior: An experimental study

Emergency signage is important for safe escape when unexpected events (such as fires) occur. However, there are limited data on the difference in the effect of emergency signage on way finding processes between individual and group conditions. This paper aims to reveal how participants alone or in groups detect and accept the information conveyed by a signage system through an experiment in buildings. One hundred nineteen volunteers participated in the experiment, which included individual and group evacuation conditions. There were six decision points along the movement path where participants could select egress routes according to signage. Posttrial questionnaires and video recordings were used to derive the number of participants whose route choice was according to signage and to derive the decision time. Results demonstrate that both signage detection and acceptance probabilities under individual conditions are larger than those under group situations, because of social influence in groups. High‐placed signs have a positive effect on route choice, especially under individual conditions. Decision time for participants whose decisions are principally according to signs is not always smaller than that for participants whose decisions are not according to signs, eg, in group situations. These findings have implications for group evacuation modeling and signage design in buildings.     

严苛条件下承压系统安全阀技术

安全阀作为承压系统主要的安全附件对保证化学与能源工业装置的安全运行起着举足轻重的作用。近年来,随着承压系统工作压力与温度环境等日益严苛,对安全阀性能也提出了更加精准与严苛的要求。为了探索先进安全阀的设计、制造与运维技术,本文概述了安全阀的研究现状和取得的重要技术进展,包括安全阀动作和排量性能的精准设计、安全阀密封设计、安全阀抗震设计、安全阀可靠性的精准设计、热态试验验证及安全阀本身的结构完整性保障和健康监测等,在此基础上,指出了今后亟待解决的若干科学技术问题,包括极端工况（高温、高压、地震、火灾等）流体流场下安全阀瞬态响应的计算模拟技术、极端工况下安全阀全性能试验装置和试验方法、精确测量安全阀流量系数的多尺度方法、智能安全阀技术、极端工况安全阀结构完整性评价技术。