We have tested a linear regression model to identify significant predictors of pre-evacuation delay in a sample of evacuees enrolled in the World Trade Center Evacuation Study. We have found that pre-evacuation delay was greater when there were more environmental cues, more seeking out of information, and more pre-evacuation actions. Additionally, higher perceived risk was predictive of shorter pre-evacuation delay times. These findings are compared and contrasted with an analysis of participants in the National Institute of Standards and Technology investigation of the World Trade Center disaster, recently reported by Kuligowski and Mileti (2009). Both studies reported factors associated with pre-evacuation delay that were similar to those associated with community evacuation. Additionally, we found that greater knowledge and greater emergency preparedness were associated with greater perception of risk. Greater emergency preparedness was negatively related to pre-evacuation delay within World Trade Center Tower I, but within World Trade Center Tower II, the relation between emergency preparedness and pre-evacuation delay was positive. These findings have implications for training of occupants of high-rise buildings.Highlights► Emergency preparedness and knowledge of the building both predicted perceived risk. ► Lower perceived risk was associated with more high-rise pre-evacuation delay. ► Predictors of human behaviors in high-rise and community evacuations are similar.
The September 11th 2001 impact on the World Trade Centre (WTC) resulted in one of the most significant evacuations of a high-rise building in modern times. The UK High-rise Evacuation Evaluation Database (HEED) study aimed to capture and collate the experiences and behaviours of WTC evacuees in a database, which would facilitate and encourage future research, which in turn would influence the design construction and use of safer built environments. A data elicitation tool designed for the purpose comprised a pre-interview questionnaire followed by a one-to-one interview protocol consisting of free-flow narratives and semi-structured interviews of WTC evacuees. This paper, which is one in a series dealing with issues relating to the successful evacuations of towers 1 and 2, focuses on cue recognition and response patterns within WTC1. Results are presented by vertical floor clusters and include information regarding cues experienced, activities prior and subsequent to occupants first becoming aware that something was wrong, perceived personal risk, time taken to respond and the inter-relationships between them. The results indicate differences in occupant activities across the floor clusters and suggest that these differences can be explained in terms of the perception of risk and the nature and extent of cues received by the participants.
The increasing accessibility of buildings to people with disabilities requires that buildings are also designed and managed to provide accessible means of escape for all. In so doing, it is important to understand the capabilities of building occupants with disabilities to evacuate and their interaction with others. This is particularly important in high-rise buildings where occupants’ primary means of accessing upper floors, i.e. lifts, may not necessarily be the preferred route in a fire emergency.
The intention of this paper is to demonstrate the feasibility of a performance-based solution for providing adequate life safety levels for the occupants of an industrial warehouse. Focus was given to the evaluation of the performance of a smoke venting system and the exit distribution in an industrial warehouse. Quantitative analyses of the available safe egress time and the required safe egress time were carried out using both a simple calculation and a computer modelling technique. The study included a sensitivity analysis to investigate multiple fire scenarios involving variations in design fires, ventilation conditions and number of exits.Computer simulations of fire growth and smoke spread in a large warehouse with a proportionally large ridge vent revealed somewhat interesting smoke movement patterns. The procedure for determining tenability in a well-ventilated high ceiling space is discussed. The result of the study demonstrated the acceptability of the alternative design solution against the established criterion. The limitations of the modelling technique and future research topics are also discussed.
Highlights are given of forty presentations and the concluding general discussion at the International Life Safety and Egress Seminar held November 23 and 24, 1981, at the University of Maryland. The seminar provided a timely opportunity for research peers, educators, designers, consultants, and standards writers to discuss egress and life safety. Participants, numbering over fifty, came chiefly from the United States, but Australia, Britain, Canada, Japan, Sweden, and New Zealand were also represented.
The meteorologic and topologic causes of the 20 October 1991 Oakland Hills conflagration are described here qualitatively. A 3 GW example fire, 100 m in diameter, is used to show the impact of the 10 m/s wind and strong inversion layer at 600 m that existed on 19 October. It is concluded that the dry, high speed NE wind, coupled with the inversion layer and the local topography channeled the hot products of pyrolysis and combustion, along with flaming debris, through a high fuel load region downwind and downslope of the initial fire, thus causing the unusually rapid initial fire spread and consequent conflagration.
In this article the various developments in the field of fire safety regarding the single European market, foreseen by 1992, are reviewed. After a brief discussion on the prospects and the needs of a European harmonization, the subject is approached from two points of view: formal aspects and technical aspects. Under ‘formal aspects’ the essence and probable impact of some European directives are discussed and a summary is given of the various initiatives which are taken to arrive at harmonized technical specifications. Under ‘technical aspects’ both scientific and practical facets of European harmonization in the field of fire safety are reviewed. The role played by Professor Pettersson in this process, is highlighted.
Fire safety and protection facilities to satisfy current regulatory requirements are a significant component in the cost of many buildings. With the development of systematic approaches to building fire safety and protection, designs based on a fire safety engineering methodology can offer substantial cost savings while achieving satisfactory levels of life safety. An outline is given of recent initiatives in Australia towards the development of a systematic approach for the design of cost-effective fire safety systems in buildings. This systematic approach is based upon a risk assessment framework. While substantial progress has been achieved, considerable research, development and technology transfer must be undertaken before this systematic approach can be used as a routine procedure for design. However, some important applications, based on such an approach, have recently been undertaken.
A cross-sectional study was undertaken in Aotearoa New Zealand to investigate the relationship between socioeconomic deprivation and risk of an unintentional fatal domestic fire incident. Addresses of unintentional fatal domestic fire incidents were geocoded to small area (census meshblock) level and analysed with the New Zealand index of socioeconomic deprivation. Fatal unintentional domestic fire incidents occurred disproportionately in dwellings in the most socioeconomically deprived meshblocks. Annual rates of fatal unintentional fire incidents per 100,000 households in the most deprived decile were significantly higher than rates in the least deprived decile (RR 5.6, 95%CI 1.9–16). Strategies to prevent fire related deaths must overcome barriers to household fire safety in population groups experiencing increased risk, including the socioeconomically deprived, seniors, and ethnic minorities. Specific intervention strategies relevant to risks associated with socioeconomic deprivation include improving quality and affordability of housing; increasing prevalence of installed and functioning smoke detectors; and regulation of specific characteristics of cigarettes to reduce risk of ignition from abandoned heat sources. Substantial progress awaits reduction of the underlying socioeconomic determinants of disadvantage.
London is a large capital city with a population of approximately seven million people. It shares many problems with other large cities around the world, including deaths due to fire. Many of these fire deaths can be linked to social problems such as poor housing, loneliness, illness, etc.Data from the London Fire Brigade Real Fire Library—a unique database of information collected from real fire incidents by dedicated teams of fire investigators operating in the Greater London Area has been used to obtain a range of statistics about fatal fires and fire death victims for the 5-year period from 1996 to 2000. Most deaths occurred in unintentional dwelling fires. The statistical information has therefore been analysed to identify the main factors involved as to why people die in unintentional dwelling fires and see what lessons can be learnt from these deaths.Common risk factors identified in the unintentional dwelling fire deaths investigated include smoking, alcohol, old age, disability, illness, living alone, social deprivation and not having a working smoke alarm fitted. Comparisons are also made with the results found from other studies and measures for preventing unintentional dwelling fire deaths are examined.
The paper presents a stochastic model for the interaction between the spread of untenable conditions and occupant egress. Safety is measured by the expected number of deaths. The building is represented by a network for modelling fire spread and by another network for modelling occupant egress. A major innovation is the introduction of the concept of discrete hazard function. It allows the interaction between the various factors involved in the spread of untenable conditions and occupant egress to be taken into account at the time of their occurrence during simulations. Two small-scale examples are worked out in detail and flowcharts for full-fledged programs are given.
In the case of fires in chemical warehouses very toxic fire effluents may be generated. Knowledge of the nature and the amount of the various combustion products is rather limited, and therefore a study has been initiated. This paper describes results obtained from combustion experiments with selected pesticides, solvents, fertilizers and polymers. The substances are: Lindane, MCPA, dimethoate, azinphos-methyl, parathion-methyl, chlorobenzene, ammonium nitrate, polypropylene, polystyrene, PVC and nylon. The DIN 53 436 furnace has been used for all experiments. The experiments have been carried out under various conditions in order to approach the simulation of different fire types. Inorganic combustion products such as carbon dioxide, carbon monoxide, nitrogen oxides, sulphur dioxide, hydrogen chloride, and hydrogen cyanide have been quantified and organic combustion products have been identified.
The use of sacrificial ablative heat shields has proved effective in protecting spacecraft on earth re-entry. However, the use of ablative coatings in the protection of structural steel appears to be limited. This paper uses a mathematical model to assess the likely effectiveness of using such a coating on steel beam sections in furnace tests. In particular, the important coating properties are identified and quantified in order to maximise the failure time (defined as the time taken for the average steel temperature to reach a preset value such as 823 K). The model produces interesting results and demonstrates that it should be possible to use coatings of moderate thickness (∼10 mm) to attain failure times of the order of 1 h, provided that other critical coating properties such as the coating Biot number, Stefan number and diffusive timescale fall within specific ranges.
When a heat release rate limit for a consumer product is set by a regulatory agency, it is of interest to know whether small excursions above that limit, such as may occur due to production line variability, represent a disproportionate increase in fire hazard. This paper presents a methodology to examine this issue. The heat release rate curve of the object is described by a Gaussian time variation; a perturbation peak, also Gaussian, is added to this main peak. The impacts of the perturbation peak on the build up of hazardous conditions in a room fire (where the object is the only item burning) and on the threat of ignition of secondary items are examined. For the peak heat release rate domain studied here, only the ignition threat is significantly affected by the perturbation peak. The results quantify the trade-off between the height of the perturbation peak and its duration for a fixed percentage of increase in the room area threatened by secondary object ignition. The results show that the increased threat is of the same order as the relative perturbation in heat release rate.
Water droplet evaporation is relevant to fire suppression, industrial cooling processes, and many other technologically important applications. A mathematical model of unsteady evaporation of a water droplet is developed. The droplet is assumed to be spherical and semitransparent to radiation. A radiative transfer model based on geometrical optics theory is used to calculate the local volumetric rate of radiation absorption. Published spectral absorption coefficient data for water are used in performing the calculations. The effects of thermal expansion and temperature-dependent thermophysical properties on the evaporation process are accounted for. The internal circulation in the droplet due to the externally imposed flow is accounted for through an effective thermal conductivity of the water droplet. The model predictions are compared with available computational results and experimental data. The results of calculations show that the absorption of radiation and thermal expansion significantly affect the lifetime of a droplet. The results also reveal that neglect of radiation absorption by a droplet underpredicts the rate of water evaporation and greatly overpredicts the droplet lifetime for droplet diameters greater than .
Quantitative approaches to estimating individual and societal risk in the nuclear industry, the chemical and fuel process industries and in building design are considered. Particular attention is paid to what have been proposed as target levels for acceptability of risk in these fields. Available data on multiple fatality fire occurrence in the United Kingdom, the United States and worldwide are examined. On the basis of this data a total societal fire risk for the U.K. is proposed. This, together with information on the number of premises at risk, allows target probabilities to be defined for premises of different size. These range from about 10−6 per annum, for premises where five or more people may be killed in a fire, to 10−7 to 10−8 per annum for premises where one hundred or more may be killed. These might be used with models of risk analysis aimed at estimating actual probabilities. These target values are compared with those used in other areas. Consideration is also given to the evaluation of the weightings used in points schemes and the development of targets of acceptability where such methods are employed.
Differing perceptions of risk by various stakeholders have long played a role in influencing the development of prescriptive-based building fire safety codes. As performance-based building fire safety codes are developed, differing perceptions of risk will continue to be a significant influence. In this paper, the concepts of revealed preference, risk factors, risk adjustment factors and risk conversion factors are discussed, and two methods to address risk perceptions in a performance-based building fire safety code are introduced. The first method proposes the use of risk factors to classify buildings in terms such as low, medium, and high risk. Each class of building would be assigned a risk adjustment factor. Similar to safety factors, risk adjustment factors would be applied during deterministic building fire safety design to provide an increased level of safety in buildings where the risk perceptions would mandate greater safety. The second method would be used with a probabilistic-based building fire safety design approach, and uses risk factors to develop risk conversion factors (RCFs). In the probabilistic approach, a maximum expected-risk-to-life (ERL) value would be established by the code, with appropriate RCFs being applied to adjust maximum ERL values depending on how the building's fire safety risk is perceived.
Experiments have been performed to study pedestrian flow through bottlenecks under oversaturated conditions. The data underline a new phenomenon in pedestrian flows: when high-density conditions occur upstream of a bottleneck, the maximum capacity of the bottleneck (i.e. the maximum number of pedestrians that can flow through the bottleneck in a given time interval) can drop. This is referred to as “capacity drop” and should be carefully taken into account when dealing with building evacuation philosophy.
During the 15-min period, or thereabouts, between the first observation of the fire and its fatal eruption into the ticket hall, the fire at King's Cross Underground Station was observed by many witnesses. Naturally, their descriptions differed appreciably in points of detail, but, overall, the led to a reasonably consistent picture of the fire's development. This picture provided a vital frame of reference against which scientific description of possible sequences of fire development could be tested, particularly with respect to the last 1 or 2 min prior to fire spread into the ticket hall.This paper presents the frame of reference provided by eyewitnesses accounts and the correlation with the outcome of the scientific investigation.
The objective of this work was to determine the accuracy and limitations of a new version of Fire Dynamics Simulator (FDS), developed by McGrattan et al., on axi-symmetric fire plumes. The current version uses LES for turbulence, a mixture-fraction-based infinitely fast chemistry model for combustion, and a constant radiative loss fraction. These sub-models have been tested for unconfined fires of different sizes, based on a dimensionless heat release rate QD* in the range of 0.1 to 10.0, which covers most natural fire scenarios. No adjustment of constants or algorithms in the model FDS2.0 have been made. An examination of plume theory is made first to find the benchmark correlations. This shows a generalization for a collection of correlations based on theory, and which might be “the best”. Using the characteristic length as the scaling factor, it is found that the optimum resolution of a pool fire simulation is around 0.05. With this resolution, the flame height prediction is found to fit well with flame height correlations. Some other parameters such as temperature and mixture fraction are found to be close to the empirical estimations at flame tips. The Froude number, which describes the relative strength of momentum and buoyancy, falls within the measurement range of many researchers. The simulation also reveals that the temperature near the burner is over-predicted, while the centerline temperature and velocity in the non-combusting region is predicted well.
In this study, the predictions of several computer fire models (CCFM, FAST, FIRST and BRI) are compared with each other and with experimental data from Australia. The experimental results were obtained by Keough (Venting Fires through Roofs, Report no. 344, Commonwealth Experimental Building Station, Australia, 1972) at Darwin airport in 1971 for relatively large fires (4 MW and 36 MW). Each model has its own virtues but no model, as yet, is consistently superior. Further work necessary for improvement of the models is discussed; hopefully, this will lead to their application to building design in the future.
The use of acoustic emission (AE) as an early indicator of structural materials exposed to a flame has been investigated and found to be possible. Piezoelectric transducers have been mounted directly on 0.5 m long, simply supported beams of aluminum, gypsum board, wood and plastic, and have been used to record ultrasonic events resulting from a small flame placed under the beam. The number of AE events in a minute and the cumulative energy released during the heating cycle provide a good measure of the overheated state of some of these materials even before a temperature increase is indicated. The measured signals varied in energy and number with the type of material, the thickness of the specimen and heat flux. Wood was particularly susceptible to acoustic emission, producing more than 1000 events/min in a solid fir board and 30/min in 13 mm thick plywood when the flame exceeded 1 kW. A gypsum board produced 16 events in a minute. An aluminum plate did not respond above the background level (0.3 events/min) even though it reached the highest temperature. The differences in cumulative energy were equally striking, with the plywood being four times more energetic than the gypsum board even though the heating period for the wood was half as long, and 30 times more energetic than the aluminum. Some critical issues which remain to be investigated before this technique can be adapted to practical fire detection are mentioned.
The phenomena observed in experimental studies on the behavior of flames propagating across flammable liquids are summarized in this paper. Since the liquid phase phenomena have been investigated extensively and already presented in several well-known review papers, the present authors have concentrated on the gas phase phenomena. It is shown that the gas motion ahead of a propagating flame is important in the mechanisms of flame propagation across a flammable liquid. The effects of wind on the behavior of a flame propagating across a flammable liquid and the flame behavior near an obstacle on the flammable liquid surface are presented. It is pointed out that a knowledge of the detailed aerodynamic structure in the vicinity of the leading flame edge is necessary to understand the effect of wind on the behavior of a flame propagating across a flammable liquid. Also, typical examples of the gas and flame front motion predicted using an inviscid theory are presented. The results imply that the flame behavior near an obstacle on the flammable liquid surface is closely related to the gas motion ahead of the propagating flame.
The various mechanisms postulated to control the rate of flame propagation across a liquid fuel surface are discussed in detail. Major consideration is given to the surface tension induced flows which control the propagation at liquid temperatures well below the closed cup flash point and the cause of the flame pulsation noted at liquid temperatures just below the flash point. Some new considerations are given to the concepts and methods of experimentally evaluating flash and fire point phenomena. Analytical developments which correctly predict the very high propagation rates across liquids at temperatures well above their flash points are discussed.
This work measures the suppression action of inert gas phase agents in extinguishing an air/liquid organic fuel pool fire. It then gives a predictive model for determining the physical contribution involved in non-inert agent fire suppression. Chemical suppression effectiveness can then be calculated. Further, studying the CF3Y and SF5Y (Y = F, Cl, Br, I) series allows quantitation of chemical suppression action of the individual radical moieties. CF3 is shown to be a strong chemical suppressant while SF5 is a flame promoter. CF3Br (Halon 1301) suppression action is 20% physical, 25% chemical due to CF3, and 55% chemical due to Br. Such quantitation provides guidance in selecting alternative fire suppressants to replace ozone layer depleting halons.
By means of series of tests carried out on simply supported beams of standard rolled sections subjected to bending, fully analytically formulated calculation values were derived for the temperature-dependent stress-strain relationships of structural steel under fire action from normal temperature to 1000 °C.Systematic series of investigations carried out on frame assemblies made up from rolled sections with high scale accuracy revealed the characteristic parameters influencing the critical temperatures. The analyses showed good-to-excellent agreement both for the temperature-displacement curves and for the critical temperatures, so that the integrity of the stress-strain relationships could also be verified for combined bending and compressive stress states and for stability-endangered assemblies.The knowledge gained by the of experiment and computation furnished — in generalized terms — a basic concept for the simple and uniform assessment of the resistance to fire action of single elements and whole assemblies of structural steel subject mainly to bending stresses or endangered in stability. This allows the collapse temperatures of uniformly heated systems to be determined as a function of load utilization factor and system slenderness. These major parameters — load utilization factor and system slenderness ratio — are normal temperature design characteristics and can be determined using conventional methods.
Twenty-four young adults were exposed twice to a smoke detector alarm activated at 60 dBA. Unlike previous studies, all subjects were unprepared for the first alarm activation (naive) and the stage of sleep in which the alarms occurred was manipulated, with the alarm being activated twice in either stage 4, stage 2 or REM sleep for each subject. Upon being woken, time estimations, dream reports, alarm interpretations and computer reaction times were collected. Five subjects (20%) did not reliably awaken to the alarms and this was associated with their reported lack of sleep the night before, and unrelated to the stage of sleep or whether it was the first or second (non-naive) alarm presentation. Of the awakening, 87% occurred within 1 min of the alarm and no differences in time to awaken were evident between the first ‘naive’ and second ‘non-naive’ awakening. When awoken by the first alarm, 95% took no action within 2 min and 92% did not correctly interpret the alarm nature of the signal. Dream incorporation was not an important variable. Estimations of time to awaken were highly correlated with actual time to awaken for the ‘non-naive’ condition. Neither time to wake across different sleep stages nor analysis of the reaction time data revealed significant differences.
This study chronicles the development and integration of a smoke detector activation algorithm (known as the SDAA) that describes the response time of a smoke detector into a large eddy simulation (LES) fire model [Roby RJ, Olenick SM, Zhang W, Carpenter DJ, Klassen MS, Torero JL. Smoke detector activation algorithm version 1 technical reference guide. NISTIR Report; 2006, in press]. Although the SDAA could be used with any CFD smoke movement model, the results here address specifically its application to the fire dynamics simulator (FDS). The fire model predicts the smoke concentration and velocity adjacent to the detector while an algorithm based on characteristic velocity-based lag times describes the transport of smoke into the sensing chamber of the smoke detector. The experimental data from a multi-room compartment fire were used for comparison and a series of benchmark studies provide a mechanism to establish the sensitivity of the model to the different input parameters. The SDAA was found to be very accurate in determining detector activation times for both high- and low-velocity smoke flows.
Conventional smoke detection in fire alarm systems is based on a measurement of either physical properties of smoke aerosols (ionization and optical detectors), temperature increase (thermal detectors) or electromagnetic radiation emitted by the fire (radiation detectors). Not much emphasis has been put on smoke gases as signatures of various types of fires. In this paper the most elementary gases produced in CEN-norm fires are qualitatively discussed in order to define levels of gas concentrations reached on time scales typical of early fire warning. Based on that information, various principles and the current state of the research and development of solid state gas sensors are presented and discussed. These are, in particular, the solid state electrolyte, the metal oxide semiconductor, the silicon semiconductor device element and, finally, the microcalorimeter. It is concluded that, with the exception of the last mentioned operating principle, solid state gas detection could provide a viable alternative or additional means for the detection of smouldering or pyrolytic fires at an early stage.
The physical basis and associated mathematical model for estimating the fire-generated environment and the response of sprinkler links in well-ventilated compartment fires with draft curtains and fusible link-actuated ceiling vents is developed. Complete equations and assumptions are presented. Phenomena taken into account include: the flow dynamics of the upward-driven, buoyant fire plume; growth of the elevated-temperature smoke layer in the curtained compartment; the flow of smoke from the layer to the outside through open ceiling vents; the flow of smoke below curtain partitions to building spaces adjacent to the curtained space of fire origin; continuation of the fire plume in the upper layer; heat transfer to the ceiling surface and the thermal response of the ceiling as a function of radial distance from the point of plume-ceiling impingement; the velocity and temperature distribution of plume-driven near-ceiling flows and the response of near-ceiling-deployed fusible links as functions of distance below the ceiling and distance from plume-ceiling impingement.The theory presented here is the basis of a user-friendly computer program, LAVENT, which is supported by a user guide and which can be used to study parametrically a wide range of relevant fire scenarios.
A generalized method is presented for determining the response time for thermally actuated sprinklers installed near the ceiling of both large and small compartments. A substitute source for the actual fire is calculated to account for the effects of a warm gas layer in the upper portion of the enclosure on ceiling-layer flow temperatures. Illustrative examples are given for the change in response time for sprinklers with RTI values of 25, 100, and , to a given fire in a series of compartments ranging in floor area from 23.8 m2 (256 ft2) to 24 300 m2 (262 000 ft2). For comparative purposes sprinkler response is also calculated for the limiting case of an unconfined ceiling.
MC additive is a new generation of additives that is being developed by our research group to improve the fire-extinguishing efficiency of water mist. MC additive not only will not corrode metal and is non-toxic to human beings, but also greatly improves the fire extinguishing efficiency. In this paper, a phenomenological study is conducted into the effect of MC additive on water mist's fire-extinguishing efficiency through the base of an ethanol fire, a diesel fire and a wood crib fire. The experimental results are explained using the chemical suppression mechanisms combined with physical suppression mechanisms.
A common technique in computational fluid dynamics (CFD) modeling of fire is to assume single step, infinitely fast combustion, in which case the transport equations of all gas species can be combined into one for a single conserved scalar called the mixture fraction. While this approach is adequate for many engineering applications, for fire scenarios that require predictions of CO formation or flame extinction, this approach is inadequate. This paper describes a method of extending the mixture fraction concept to address two-step chemistry. The two-step chemistry allows for flame extinction and the prediction of CO formation and destruction. The mixture fraction is decomposed into components representing the states of the two-step chemistry. The new model is demonstrated with two test cases: a slot burner using direct numerical simulation (DNS) and a reduced scale enclosure using large eddy simulation (LES). Results of the new model are compared with experimental data and simulations using single-step chemistry.
For multi-storey buildings, structural steel members may be used to provide vertical and lateral support. These members may be incorporated within fire-resistant enclosures that are provided to house elevators, stairs and other services. In the case of elevator shafts, structural members located within the shaft are usually required to achieve high levels of fire resistance, despite the fact that they are located within fire-resistant enclosures. Such requirements appear to be unnecessarily onerous, imposing a financial burden on developer and owners. This paper considers this issue and presents the results of some full-scale fire tests undertaken to directly investigate this matter. The outcomes of these tests and the discussion of factors presented in this paper provide useful data and background to assist the fire-engineering assessment of this situation. Such an assessment will be necessary where it is intended to utilise unprotected steel construction or structural members within elevator shafts which have a lesser level of fire resistance than that required by the prescriptive regulations.
This work provides new experimental data to characterise entrainment of air into adhered thermal spill plumes using physical scale modelling. For the two-dimensional plume, the rate of entrainment with respect to height of rise is approximately half that of an equivalent two-dimensional balcony spill plume. For the three-dimensional plume, the rate of entrainment appears to be linked to the plume behaviour, which has been characterised in terms of the width and depth of the layer flow below the spill edge. In general, a layer flow below the spill edge that is shallow compared to its width will tend to adhere to the wall above the opening compared to flows whose depth approaches its width. This work proposes new empirical entrainment design formulae that have been developed on a more general basis compared to existing methods.
The key to the solution of fire safety design problems is the capability to predict the dynamics of enclosure fire environments. This paper presents a detailed qualitative description of the generic phenomena which occur during typical fire scenarios. The focus of attention is on effects within building compartments of fire involvement, i.e., compartments made up of a single enclosed space or a space of two or more rooms interconnected by significant penetrations such as open doors or windows. Throughout the discussion reference is made to quantitative methods for predicting some of the most significant of these effects. Reference is also made to available mathematical/computer models which use these latter methods to quantitatively predict the overall fire environment.
With the global move towards performance based fire design, fire safety assessment in and around buildings becomes increasingly important. However, key knowledge gaps still exist concerning the behavior of fire swirling, which may be generated if one or more accidental fires are in the passage of the vortices behind an adjacent tall building. The present study is focused on the experimental investigations of the burning behavior of two pool fires behind 1/50 scaled tall buildings with heights varying from 0.565 to 1.165 m in a cross-wind. The objective is to gain insight of the effect of the distance between the two fires (D2), the distance between the fires and the building (D1), wind speed (V), and the height of the scaled building (H) on the burning behavior. Important conclusions have been drawn about the influence of D1 and D2 on the fuel mass loss rate, the influence of D1 on fire swirling, the influence of D2 on the possible merging of the two fires and the effect of wind speed on the mass loss rate. The results suggested the existence of a critical velocity for the cross-wind on the initiation of fire swirling and an approximate value was identified for the conditions in the tests. The investigations also covered the effect of height of the scaled building on the fuel mass loss rate and the occurrence of fire swirling. This relationship was found to be also dependent on the wind speed. Analysis of the results has led to some important recommendations to enhance the fire protection of tall buildings.
Reducing access to ignition materials such as matches and lighters is a standard part of most interventions to reduce juvenile firesetting, but children of all ages are still permitted to purchase ignition materials, such as matches and lighters, from retail outlets. This brief research report describes the costs and consequences of the misuse of retail-obtained ignition materials by children and youth. This study shows that almost a fifth (18%) of children and adolescents referred to a specialized juvenile fire-starting program had used ignition materials that they obtained from retail outlets in their fire-starting. Moreover, their fire-starting was extensive and had caused or had the potential to cause significant injuries. In addition, their fire incidents were costly in terms of damage and community resources. Implications for fire safety education for retailers, further research, and legislative action are discussed.
This paper is concerned with the development of an advanced analysis numerical tool capable of estimating the inelastic large-displacement behaviour of plane steel-framed structures under fire conditions. A non-linear transient heat transfer analysis is performed on the basis of the finite element method (FEM), following the main guidelines proposed by the European Code for steel structures under fire conditions. The computational analysis program is used to assess the structural load-bearing functions and to estimate the structural behaviour and the corresponding time-resistance period. The original refined plastic hinge method is extended for fire design analysis considering both tangent modulus model and inelastic stiffness degradation concepts in the developed computational program. A tangent modulus model is developed for the European column buckling-curve for fire condition. A gradual inelastic surface is proposed as a function of the temperature and the loading combination. The results obtained are compared with those from an FEM computational program and those from the Eurocode simplified design recommendations. The benefits of using steel ductility in the current design of fire-unprotected structures are outlined.
The objective of this work was to assess the feasibility of reducing false alarms while increasing sensitivity through the use of combined conventional smoke detectors with carbon monoxide (CO) sensors. This was accomplished through an experimental program using both real (fire) and nuisance alarm sources. A broad selection of sources was used ranging from smoldering wood and flaming fabric to cooking fumes. Individual sensor outputs and various signal-conditioning schemes involving multiple sensors were explored.The results show that improved fire-detection capabilities can be achieved over standard smoke detectors by combining smoke measurements with CO measurements in specific algorithms. False alarms can be reduced while increasing sensitivity (i.e., decreasing the detection time for real fires). Patented alarm criteria were established using algorithms consisting of the product of smoke obscuration and the change in CO concentration. Alarm algorithms utilizing ionization detector smoke measurements proved to be more effective than measurements from photoelectric detectors.
One of the recommendations of the National Construction Safety Team (NCST) for the Federal Building and Fire Safety Investigation of the World Trade Center Disaster [NIST NCSTAR 1 Final report on the collapse of the World Trade Center Towers. NCST for the Federal Building and Fire Safety Investigation of the World Trade Center Disaster, National Institute of Standards and Technology, Gaithersburg, MD, September 2005] is to enhance the capability of available computational software to predict the effects of fires in buildings, for use in the design of fire protection systems and the analysis of building response to fires. Following this recommendation, this paper presents two new interfaces in fire–thermal–structural analysis. The first interface uses adiabatic surface temperatures to provide an efficient way of transferring thermal results from a fire simulation to a thermal analysis. It assigns these temperatures to surface elements of structural members based on proximity and directionality. The second interface allows the transfer of temperature results from a thermal analysis modeled with solid elements to a structural analysis modeled with beams and shells. The interface also allows the reverse, namely the geometric updating of the thermal model with deflections and strains obtained from the structural analysis. This last step is particularly useful in intense fires of long duration, where significant deflections and strains could cause damage to insulation and displace the structure to a different thermal regime. The procedures can be used for a variety of fire simulation, thermal, and structural analysis software.
Some recent studies concerned with fire physics in Japan are considered. The studies are classified in two groups, one which deals with fire in its broad sense and includes mathematical fire modeling, model experiments, studies on an overall characterization of fire, and a statistical approach: the other group includes research projects to clarify particular aspects of fire which may lead to improvements in the sub-programmes of fire modeling. The involvement between phenomenological fire research and the systems approach to fire safety design is also discussed.
In this paper, the term ‘assessment method’ implies a broad class of standardized experiments which are used in the process of evaluating the fire safety of materials, products or systems. A subset of methods exists which has traditionally been referred to as ‘fire tests’. A brief history of full-scale and bench-scale fire tests is presented. A framework for evaluating the fire performance of building elements, assemblies, contents or materials is described and used to discuss the recent advances in fire tests. The role of fire scenarios is discussed in the context of assessment methods. The continuing theme throughout the paper is the impact of the oxygen depletion method of measuring the rate of heat release, one of the most important advances in the assessment of fire safety during the past 15 years. Corner tests of wall coverings including the effects of changing ‘stand off’ distance between ignition source and the wall of a corner test are discussed. Representative data from a series of different experiments are given to illustrate the use of corner tests. A concept of the critical ignition energy to cause propagation is introduced.
Optical detection principles play an important role in automatic smoke detection systems. Significant optical properties of an aerosol can be determined from angle- and polarization-dependent light-scattering experiments.A simple instrument was built to continuously monitor the polarized scattering cross-sections of aerosols. Two solid-state diode lasers with orthogonal polarization vectors serve as light sources. They emit light at a wavelength of 690 nm, and their light emissions are modulated at frequencies of 4 and 5 kHz, respectively. Fourteen photo detectors are arranged on one half of an annulus 30 cm in diameter. Each detector simultaneously measures the scattered-light intensities for both polarizations. After demodulation and separation of the two signals by a lock-in technique, the signals are filtered, amplified, and sampled with a time resolution of 1 s. The flat and open mechanical outline of the apparatus is well suited for direct measurements on the ceiling of a fire laboratory since it does not interfere with the natural aerosol convection.Comparisons between aerosols from test fires conforming to the European standard EN54 and aerosols not originating from combustion processes (water vapour, oil vapour) were carried out. Back calculations of the aerosol size distribution from measured data are demonstrated for latex test aerosols.
U.S. Navy air-capable ships require the staging of weapons near superstructures, which results in a fire and explosion hazard to mission-critical flight operations areas. An aqueous film-forming foam (AFFF) fire suppression system was designed and tested which will rapidly control a flammable liquid-fuel spill fire in the weapons staging area. Factors which influenced the design of the system included limited available water and AFFF supply, severe wind conditions which dramatically change AFFF spray pattern coverage, and cooling requirements to prevent weapons explosions. The resulting fire suppression system utilizes AFFF discharged through non-air aspirating spray nozzles located near the weapons staging area deck. Data and results of testing may have other aviation fire safety applications.
Drainage measurements are commonly used for assessing the quality, water-retention ability and stability of aqueous foams used in fire-fighting applications. A new experimental technique is proposed in this paper, for measuring the drainage rate of liquid from compressed-air fire-fighting foams. The procedure outlined here provides advancement in precision over that prescribed by the standard for low expansion foams (NFPA 11, Standard for evaluating low expansion foams, NFPA, Quincy, MA, 1998). A comparative analysis of drainage characteristics in two commonly used Class B fire-fighting foams was undertaken, from theoretical and experimental perspectives: (i) aqueous film forming foam and (ii) film forming fluoroprotein foam. It is demonstrated that even though both the foam solutions exhibited similar fundamental physical properties, the disparities in surface rheological properties cause the resulting foams to have remarkably distinct drainage and coarsening characteristics. In addition, a drainage model is outlined, which allows the explicit prediction of the time evolution of liquid holdup profiles and drainage rates in fire-fighting foams. The existing drainage model is extended to simulate fire-fighting foams made from protein based and synthetically produced surfactants.
Computational fluid dynamics (CFD) calculations were carried out to design total flooding fire tests in a 28 m3 compartment for an ultra fine water mist (<10 μm). The exit momentum of the mist produced by a proprietary ultrasonic generator technology was extremely low with a mist discharge velocity below 1 m/s. The mist was discharged with multiple floor outlets equally spaced around the centrally located 120 kW pool-like gas fire. The transport of mist and its interaction with the fire was simulated by Fluent, a commercial CFD model. Lagrangian Discrete Phase Model (DPM) was used for droplets. Simulation predicted extinguishment within 10 s with a mist delivery rate of 1 l/min. However, in total flooding fire tests conducted, extinction times were more than 5 min. Additional computations approximating the ultra fine mist (UFM) as a dense gas agreed well with the observed transport timescales of minutes indicating that UFM behaves like a gas. Further, the mist–fire interaction needs a multi-phase Euler–Euler approach with a droplet vaporization model.
The design, construction, demonstration, and operation of a bench-scale device capable of comparison screening the fire suppression efficiency of liquid agents are described in this paper. The apparatus is based on a well-characterized flame, a means to facilitate the introduction of liquid agents, and a way to generate liquid droplets. A porous cylinder in a counterflow diffusion configuration is used. A small-scale vertical wind tunnel, which allows for the delivery of a uniform flow of oxidizer to the burner and also assists in the delivery of liquid agent droplets to the flame, is used for the flow facility. Droplets are generated by a small glass nebulizer. The performance of the screening apparatus was evaluated using several liquid fire suppressants with different thermophysical properties. A test protocol is also proposed.
Soot processes within hydrocarbon/air diffusion flames are important because they affect the durability and performance of propulsion systems, the hazards of unwanted fires, the pollutant and particulate emissions from combustion processes, and the potential for developing computational combustion. Motivated by these observations, this investigation involved an experimental study of the structure and soot properties of round laminar jet diffusion flames, seeking an improved understanding of soot formation (growth and nucleation) within diffusion flames. The present study extends earlier work in this laboratory concerning laminar smoke points (l) and soot formation in acetylene/air laminar jet diffusion flames (2), emphasizing soot formation in hydrocarbon/air laminar jet diffusion flames for fuels other than acetylene. In the flame system, acetylene is the dominant gas species in the soot formation region and both nucleation and growth were successfully attributed to first-order reactions of acetylene, with nucleation exhibiting an activation energy of 32 kcal/gmol while growth involved negligible activation energy and a collision efficiency of O.53%. In addition, soot growth in the acetylene diffusion flames was comparable to new soot in premixed flame (which also has been attributed to first-order acetylene reactions). In view of this status, a major issue is the nature of soot formation processes in diffusion flame involving hydrocarbon fuels other than acetylene. In particular, information is needed about th dominant gas species in the soot formation region and the impact of gas species other than acetylene on soot nucleation and growth.
New plume formulations have been developed for assessing air entrainment into thermal plumes that spill over a balcony edge into an atrium void.A simple weak rectangular plume treatment is developed to incorporate the effects of entrainment into plume ends. This is shown to be asymptotic to two dimensional, line plume (near the balcony) and three dimensional axisymmetric plume limits (in the far field).In addition a strong curved plume analysis that also includes the influences of the horizontal momentum of the smoke layer at the balcony edge is developed. The results of the analytical formulations have been compared with Harrison’s new comprehensive experimental data  and with CFD predictions from the JASMINE CFD model. It is shown that a virtual line source located a distance approximately three layer depths below the balcony edge provides a reasonably good description of mass fluxes for plumes with and without end entrainment.It is concluded that for practical engineering application, a simple rectangular plume treatment describes the transition from two- to three dimensional flow sufficiently well to be a simple option for the inclusion of end effects.