Post-flashover Fire Research Articles

Fire and Rescue Services Reconfiguration for Better Dealing with Post-Flashover Building Fires

The reconfiguration of fire and rescue services is the focus of this research. The main purpose is to propose an alternative organizational model for better dealing with post-flashover building fires. The primary source of empirical information is a survey involving 267 managers from the Bulgarian fire and rescue services to gather insights. The research methodology meticulously encompasses the identification of changes concerning the efficiency and effectiveness of the fire and rescue services, the discernment of inherent challenges, the definition of specific factors and criteria relevant to their activities, and the determination of strategic priorities. The goal is to suggest a new, more efficient way to organize these services in Bulgaria, whose approach can be applicable to other contexts in similar conditions as well. The proposed model suggests that the Bulgarian fire and rescue services should work independently from the Ministry of Interior as the State Agency under the Council of Ministers. In addition, a comparison between this newly proposed model and the current one is conducted to highlight its potential advantages.

Defining the fire decay and the cooling phase of post-flashover compartment fires

The current research study discusses and characterises the fire decay and cooling phase of post-flashover compartment fires, as they are often mixed up despite their important heat transfer differences. The two phases are defined according to the fire heat release rate time-history. The fire decay represents the phase in which the fire heat release rate decreases from the ventilation- or fuel-limited steady-state value of the fully-developed phase to fire extinguishment. This phase is highly influenced by the fuel characteristics, ranging from fast decays for hydrocarbon and liquid fuels to slow decays for charring cellulosic fuels (wood). Once the fuel is consumed, the compartment volume enters the cooling phase, where the cooling in the gas-phase and solid-phase happens with significantly different modes and characteristic times. The thermal boundary conditions at the structural elements are then defined according to physical characteristics and dynamics within the compartment. The research study also underlines how the existing performance-based methodologies lack explicit definitions of the decay and cooling phases and the corresponding thermal boundary conditions for the design of fire-safe structural elements under realistic fire conditions.

Application of the Framework for Fire Investigations in Informal Settlements to large-scale real fire events – Consideration of fire formation patterns, fire spread rates and home survivability

In recent years, there has been a growing number of projects on informal settlement (IS) fire research, which has been primarily focused on understanding the fire dynamics in IS through full-scale experiments. However, much less is known about real IS fire incidents. Recently, a Framework for Fire Investigations in Informal Settlements (FFIIS) was developed. However, the FFIIS has not been applied to real IS fire incidents yet. This paper seeks to conduct fire investigations by applying the FFIIS to three real fire events. One of them was recorded by a CCTV camera and was analysed in depth in previous work. The video footage was used to benchmark the findings obtain using the FFIIS. The application of the FFIIS allows one to develop hypotheses that more accurately define the area of fire origin and pattern formation sequence. This implies that the fire pattern for large post-flashover fires in ISs can be treated as wildland fires pattern, as proposed by the FFIIS. Additionally, spread rates and the impact of dwellings’ separation distances, in these incidents, are studied. Understanding the limitations and the quality of the information that can be obtained when applying the FFIIS is fundamental to improve the guidelines proposed.

Development of a full-scale testing methodology for benchmarking fire suppression systems for use in informal settlement dwellings

Informal settlements (also referred to as slums, shantytowns or squatter camps) are expanding at a rapid rate with more than a billion people currently residing in informal settlements worldwide. The dwellings within these communities are often constructed from readily available materials, making them susceptible to large conflagrations. Within the South African context, there is significant political pressure on governmental agencies to develop and implement interventions to suppress informal settlement fires. However, many proposed solutions lack a sound scientific validation. This paper proposes a full-scale fire testing methodology for benchmarking various suppression systems against each other, using a representative informal settlement dwelling. The aim of the methodology is to assist decision-making when assessing which interventions will be most suitable in post-flashover informal settlement fires. The testing methodology can be carried out without the need for sophisticated equipment, making it readily available to fire brigades and municipalities. In this work a total of nine experiments were conducted which included: brigade-based, community based as well as non-water-based interventions. It was observed that the water-based interventions typically outperformed the remaining interventions, since they suppressed the fire while simultaneously providing a cooling effect, thereby lowering the temperature within the dwelling below the auto-ignition temperature of the fuel, thus preventing re-ignition from occurring. A model is proposed for comparing the efficacy of products based upon the analytical hierarchy process. The results from these types of tests could be adopted as a decision-making tool by the respective authorities thereby potentially preventing costly investments in products that are not suitable for the cause.

Fire resistance of cold-formed steel framed shear walls under various fire scenarios.

This paper presents results of large-scale experiments with varying levels of fire severity on lateral force-resisting systems commonly used in cold-formed steel framed buildings. Gypsum-sheet steel composite panel sheathed walls, oriented strand board sheathed walls, and steel strap-braced walls are examined. Postflashover fire conditions of two different intensities as well as 1 hour of fire exposure similar to that in a standard furnace qualification test are studied. Additionally, a full-scale furnished kitchen fire experiment is conducted for comparison. The results highlight differences in the thermal response and subsequent performance of the walls as well as differing sensitives of the walls to pre-damage, eg, that might occur during an earthquake. The results are part of a larger effort to provide fragilities for these wall systems in response to realistic fires for performance-based design.

Fire Temperature Based on the Time and Resistance of Buildings—Predicting the Adoption of Fire Safety Measures

During a fire in enclosed spaces, having structures with a good level of resistance is very important. The post flashover fire time interval, during which rescue squads operate, is important to verify if the structure can still resist fire for an acceptable time interval. This can be determined through the REI value. Hence, the way the fire develops must be examined together with the trend of the temperature that might guarantee that the structure will resist the heat flux released during the combustion. This article examines and compares, through a case study, the most important methods for analysis of the fire risk: the prescriptive approach and the simplified performance-based approach. The performance-based method (more suitable for the actual planning demand with respect to the more cautious prescriptive approach) is affected by the parameters influencing its development. The goal of this article is to provide a graph (based on parameters like the type of building, opening factor “O” and fire load “q”) that might be used by designers and architects to carry out the planning phase and adopt fire prevention systems before dealing with the assessments required by the engineering field for the fire risk analysis.

Testing Method for External Cladding Systems - Incerc Romania

This research presents a new testing method in a natural scale for external cladding systems tested on buildings with minimum than 3 floors [1]. The testing method is unique in Romania and it is similar about many fire testing current methods from European Union states. Also, presents the fire propagation and the effect of fire smoke on the building façade composed of thermal insulation. Laboratory of testing and research for building fire safety from National Institute INCERC Bucharest, provides a test method for determining the fire performance characteristics of non-loadbearing external cladding systems and external wall insulation systems when applied to the face of a building and exposed to an external fire under controlled conditions [2]. The fire exposure is representative of an external fire source or a fully-developed (post-flashover) fire in a room, venting through an opening such as a window aperture that exposes the cladding to the effects of external flames, or an external fire source. On the future, fire tests will be experimented for answer demande a number of high-profile fires where the external facade of tall buildings provided a route for vertical fire spread.

Distributive Analysis of Temperature Variation According to Fire Patterns through Burn Test

본 연구는 열전대 29개와 데이터록, 그리고 열화상 카메라 등 첨단장비를 활용한 연소실험을 통하여 화재패턴의 영향요인/변수 중 하나인 플래시오버(flashover)를 중심으로 플래시오버 이전단계(preflashover)와 플래시오버 이후단계(post-flashover) 상황으로 구분하여 실험을 전개하였다. 열전대 실험에서 U패턴과 역콘형 패턴을 위시하여 V패턴, 완전 연소, 포어패턴(pour pattern), 엘리게이터 탄화패턴(alligator char pattern), 보호구역 및 열 그림자 그리고 폴다운패턴(fall down pattern)에 대하여 각각 관찰하였다. 또한, 과학적인 데이터 수집과 그 분석 자료에 기초하여 실제 화재조사 현장실무에 적합한 새로운 조사이론과 아이디어를 개발하고자 열전대 및 열화상 데이터 자료에서 수집한 화재패턴과 온도변화의 분포 비교를 통하여 화재패턴 형성과정에 따른 온도의 변화를 검토하였다. 특히, 열전대 데이터에서는 화재기둥과 공기유입의 상관관계 이론을 기초로 컨테이너 구획실의 코너와 벽에서의 화재기둥온도 900℃ 및 1,300℃를 비교 분석한 결과, 내부에서 방화에 의한 비정상 연소를 입증할 수 있었다.This research paper is to study on an analysis for fire pattern’s change in temperature and use of their tests data through combustion experiments using state-of-the art device such as 29 Thermocouples, a Data Logger, and Infrared Thermal Camera. Burn pattern test have been conducted in the phase of pre-flashover fire and post-flashover fire. In the thermocouple experiment, the U pattern and the inverted cone pattern are used and the V pattern, the clean burn, the pour pattern, the alligator char pattern, the protection zone and the heat shadow and the fall down pattern were observed. In addition, to develop new research theories and ideas that are appropriate for practical fire investigations on the basis of scientific data collection and analysis data, the change of temperature according to the process was examined by comparing fire patterns and temperature variations collected from thermocouples and thermal image data. In particular, from thermocouple data and intensity patterns from fires, these tests have determined that the burn have become intense and have the highest temperature (1300℃) when near a floor against wall at a main gate, compared to that of corner (900℃) in experiment sets.

Detection of Skeletal Trauma on Whole Pigs Subjected to a Fire Environment

Fire can cause alterations in bone stability and composition that may impact an anthropological analysis of skeletal morphology and trauma. In this study, the extent that fires of different duration and intensity affected trauma analyses during a compartment fire was tested This study incorporated on site scene analysis to examine the significance of trauma identifications from burnt bodies in forensic cases and the impact that fire investigation plays on the ability to recognize, preserve, and analyze skeletal elements from burned remains. Whole pig carcasses were subjected to sharp force, blunt force, and gunshot trauma to investigate the influence of intense fire conditions on these injuries. The perimortem trauma marks were then assessed in relation to their exposure in a compartment fire that progressed through flashover conditions. This study found that fire can differentially influence an analyst’s ability to recognize and analyze wounds in the limbs vs the torso but was still recognizable and often protected in the postcranial body. Highlights: • Skeletal trauma impact marks survivability in post-flashover fire conditions; • Postcranial trauma protected by soft tissue post flashover; • Fire related skeletal trauma differs from sharp force, blunt force, and gunshot trauma.

Toxic Combustion Product Yields as a Function of Equivalence Ratio and Flame Retardants in Under-Ventilated Fires: Bench-Large-Scale Comparisons.

In large-scale compartment fires; combustion product yields vary with combustion conditions mainly in relation to the fuel:air equivalence ratio (Φ) and the effects of gas-phase flame retardants. Yields of products of inefficient combustion; including the major toxic products CO; HCN and organic irritants; increase considerably as combustion changes from well-ventilated (Φ < 1) to under-ventilated (Φ = 1–3). It is therefore essential that bench-scale toxicity tests reproduce this behaviour across the Φ range. Yield data from repeat compartment fire tests for any specific fuel show some variation on either side of a best-fit curve for CO yield as a function of Φ. In order to quantify the extent to which data from the steady state tube furnace (SSTF [1]; ISO TS19700 [2]) represents compartment fire yields; the range and average deviations of SSTF data for CO yields from the compartment fire best-fit curve were compared to those for direct compartment fire measurements for six different polymeric fuels with textile and non-textile applications and for generic post-flashover fire CO yield data. The average yields; range and standard deviations of the SSTF data around the best-fit compartment fire curves were found to be close to those for the compartment fire data. It is concluded that SSTF data are as good a predictor of compartment fire yields as are repeat compartment fire test data.

Robustness assessment of a generic steel fire-protected moment-resisting frame under travelling fire

Due to their vulnerability to high temperatures, steel structures are typically protected against fire by insulation materials, as recommended by fire codes. The fire resistance rating of a protected member is determined based on a standard fire test, which simulates post-flashover fire conditions. Empirical evidence has shown that fires in large open-plan compartments do not burn uniformly, and a method called “traveling fire” has been introduced in previous research to simulate the effects of spreading fires. An investigation is performed here to examine the robustness of a generic four-story moment-resisting steel structure with one-hour fire resistance rating subjected to travelling fire. Various fire sizes are considered: 12.5, 25, 50 and 100% of the floor area. The results show that while no collapse occurs during the 12.5, 50 and 100% fire sizes, the structure collapses under the 25% fire size at 85 min due to the inability of the system to transfer the load after one of the columns buckles. This seems to be in contradiction with traditional belief that a fire covering a larger portion of the floor plan would reduce the safety margin. The investigation performed underlines that the fire protection of structures based on the standard time-temperature curve does not necessarily provide adequate resistance under travelling fires. With the lack of adequate fire regulations codified for large compartments, more research is required before arriving at a better understanding of the application of travelling fire to large compartments.

Large eddy simulation of post-flashover room fires based on the Vreman subgrid-scale model

Since the Vreman subgrid-scale model was proposed, different types of flow fields have been used to research the applicability of this model. However, the applicability of the model to a flashover heat flow field simulation and the optimal model coefficient for room fires have not been reported. In this paper, the flashover room fire experiments of different opening sizes (ventilation factor) are conducted in an experimental room of size similar to ISO9705, and the room temperature at typical locations is measured. On the same numerical simulation platform, the room temperature field is simulated numerically using the large eddy simulation based on the Vreman and Smagorinsky subgrid-scale models. When the ventilation factors are 1.932 and 2.178, a Vreman subgrid coefficient of 0.02–0.04 is more applicable to the simulation of the temperature field. Overall, the simulation results of the maximum temperature based on the Vreman subgrid-scale model are slightly better than that of Smagorinsky subgrid-scale model. Moreover, the simulation result of the temperature change according to the time from the Vreman subgrid-scale model is similar to the experimental result. However, near the corner of the door in the room, the numerical simulation results underestimate the maximum flow field temperature in the room’s upper part. When the Vreman subgrid-scale model simulates the temperature field in the room with a subgrid coefficient of 0.04 and a ventilation factor of 2.263, the simulation results are better than the results from the Smagorinsky subgrid-scale model with a subgrid coefficient of 0.2. However, when the ventilation factor is 1.397 and the opening is relatively small, the large eddy simulation result based on the Vreman subgrid-scale model with a subgrid coefficient of 0.04 is worse than the results based on the Smagorinsky subgrid-scale model with a subgrid coefficient of 0.2.

Effects of Combustible Stacking in Large Compartments

This paper focuses on the modelling of fire in case of various distributions of combustible materials in a large compartment.Large compartments often represent a challenge for structural fire safety, because of lack of prescriptive rules to follow and difficulties of taking into account the effect of non uniform distribution of the combustible materials and fire propagation.These aspects are discussed in this paper with reference to an industrial steel building, taken as case study. Fires triggered by the burning of wooden pallets stored in the premises have been investigated with respect to different stacking configurations of the pallets with the avail of a CFD code. The results in term of temperatures of the hot gasses and of the steel elements composing the structural system are compared with simplified analytical model of localized and post-flashover fires, with the aim of highlighting limitation and potentiality of different modelling approaches.

Air pumping action of a plume in a room fire

Air pumping effect of a fire plume to give higher intake rate through vertical openings in a post-flashover room fire will be discussed in this paper. The thermal balance equation was set up with known fire phenomena in a room. The hydrostatic model was applied to study the air intake rate through vertical openings. An equation relating heat release rate to room air temperature rise with empirical constants was then justified by reported experimental data on post-flashover room fire. The heat release rate was measured by the oxygen consumption method in that experiment. The predicted heat release rate from the empirical equation reported in the literature was observed to be proportional to the room air temperature rise as derived from hydrostatics. However, the proportionality constant is lower than the experimental value. A possible explanation is due to neglecting another fire phenomenon on air pumping action of the fire plume in a real room fire. Higher pressure differences across the door would give higher airflow rates across an opening. This would supply more air to give higher heat release rate as observed in the experiment. In this paper, the pressure due to air pumping of the fire plume is taken as a proportion of the hydrostatic pressure due to temperature differences between the upper hot layer and lower cool layer. Comparing the measured heat release rate with the estimated heat release rate due only to hydrostatics will give the air pumping action. The possible increase in heat release rate in a post-flashover fire can then be estimated accordingly.

Detailed study of distribution patterns of polycyclic aromatic hydrocarbons and isocyanates under different fire conditions

This study has examined the distribution patterns between gas phase and particle phase of some chemical compounds produced in fires. It has also addressed the question of the distribution of individual particle-associated species between the different size-ranges of particles. The chemical compounds studied and discussed in this paper are polycyclic aromatic hydrocarbons (PAHs), and isocyanates. The steady-state tube furnace, ISO/TS 19700, was chosen as the physical fire model in order to study the production of particles from different types of fire exposure, that is, oxidative pyrolysis, well-ventilated flaming fires and under-ventilated flaming post-flashover fires. Two materials were chosen for investigation, a polyvinyl chloride (PVC) carpet and a wood board. The particle production from the two materials investigated varied concerning both the amounts produced and the particle size distributions. The analysis of PAHs showed that volatile PAHs were generally dominant. However, when the toxicity of the individual species was taken into account, the relative importance between volatile and particle-associated PAHs shifted the dominance to particle-bound PAH for both materials. The substantial degradation in the tests of the low polyurethane content of the PVC carpet, and the (4,4′-methylenediphenyl diisocyanate)-based binder in the wood board resulted in no or very small amount of quantifiable diisocyanates. Copyright © 2013 John Wiley & Sons, Ltd.

Modeling fire-induced radiative heat transfer in smoke-filled structural cavities

Accurate heat transfer prediction is important to structural fire engineering in order to analyze thermal–mechanical behavior of structures in fire. However, the presence of cavities and participating media complicates radiative calculations. A numerical approach with finite element and discrete ordinates method is presented in this paper to predict fire imposed radiative heat fluxes to these type of structural members. This approach is used to simulate heat transfer to unprotected steel I-sections with symmetrical cavities exposed to post-flashover fires. Results show that the cavity geometry could strongly attenuate the radiative energy, while the presence of hot smoke enhances radiative transfer by emission. Average radiative fluxes for inner surfaces of the I-sections are seen to increase with smoke opacity. In addition, the radiative fluxes are observed to decrease faster for I-sections with higher section factors. This work also shows that the self-radiating mechanism of I-sections is important in the optically thin region, and existing methodologies neglecting these physics could significantly underpredict steel temperatures.

Temperature of a partially embedded connection subjected to fire

When subject to fire, structural steel and connectors lose both their strength and stiffness. Structures expand when heated and contract on cooling. Furthermore, the effect of restrained thermal movement can introduce high strains in both the steel member and the associated connections. Fire tests on steel structures have shown that the temperature within the connections is lower compared to the connected steel members. The beneficial effect of the partial embedding of a connection in a concrete slab for its resistance in fire conditions was already intuitively utilised by structural engineers. Three sets of tests provide the measuring of the accuracy of the developed numerical and analytical model for heat transfer and temperature distribution in the partially embedded connections. The connection shadow factor is proposed further to allow the prediction of temperatures in connections from the calculated gas temperature during a post-flashover fire.

An improved two-layer zone model applicable to both pre- and post-flashover fires

The present paper proposes a sub-model for two-layer zone models to describe heat and mass transfer across the interface between the upper and lower layers as a result of the temperature difference between the two layers. The sub-model is integrated into a two-layer zone fire growth and smoke movement model, which now can predict both pre- and post-flashover fires. The comparison of the numerical predictions of the improved model and experimental data shows that the improved model produces better temperature and heat release rate predictions for both pre- and post-flashover fires than the previous model. Compared with hybrid models consisting of a two-layer zone model and a single-layer zone model, the improved model has no transitional difficulties in switching from the pre- to the post-flashover state and it produces more reasonable temperature gradients for post-flashover fires.

Global modelling of fire protection performance of an intumescent coating under different furnace fire conditions

This article presents a method to model the overall fire protection performance of an intumescent coating under different post-flashover furnace fire conditions. Intumescent coatings are reactive fire protection materials, and their fire protection performance, among which the maximum expansion ratio is the key indicator, depends on the heating condition. The aim of this research is to find one common set of properties to enable the intumescent coating fire protection performance to be predicted across different heating conditions on the intumescent coating. The obtained properties are implemented in a model to predict the global expansion process of intumescent coating and the protected steel substrate temperature under various furnace temperature–time curves. This model has previously been demonstrated by the authors to provide accurate results for cone calorimeter tests under different levels of radiant heat flux (50 and 65 kW m−2) and with different combinations of steel plate thickness (5, 10 and 20 mm) and intumescent coating dry film thickness (0.4, 0.8 and 1.2 mm). This article will present the experimental results of post-flashover furnace fire tests under different fire temperature–time relationships (slow, fast and standard) for the same combinations of steel plate thickness and dry film thickness as used in the cone calorimeter tests. A comparison between the prediction and experimental results indicates that the steel plate temperature results are typically within 10% and the final expanded thickness within 20% of each other.

Experimental study and modeling of radiation from compartment fires to adjacent buildings

This paper presents twelve full-scale experiments conducted on radiation from compartment fires to a target wall. The impact of different window sizes, separation distances between the fire building and a target wall, and different fuels on radiation heat fluxes on target wall is investigated. The contribution of external flame to radiation heat flux on target wall was studied. The emissivity of external flame is analyzed which shows that the experimental value is larger than that suggested by previous studies. The experimental data have been compared with theoretical results. The discrepancy between experimental and theoretical data has been explained. The limitations and recommendations of some equations have been discussed. Furthermore, a modeling of radiation heat flux on target wall from post-flashover compartment fire is proposed. This work is expected to be used as the basis to develop modeling of fire spread between buildings, modeling of post-earthquake fire spread and modeling of urban/wildland interface fire spread.