Emissions from Fires Part II: Simulated Room Fires

Detailed quantitative characterization of the combustion gases from a series of room fires is reported in this article. Three simulated room fires were conducted with a test room containing a typical domestic fuel load of furniture including a TV-set. Two types of TV-sets were studied in the experiments, i.e. those containing fire retarded and non-fire retarded enclosure material. The measurement of the combustion gases included inorganic species and various organic species among them polychlorinated and polybrominated dibenzodioxins and furans, and selected brominated flame retardant agents. The detailed quantitative characterization of the combustion gases from the room fires forms a unique source of emission data for fire incidents in buildings. Chlorinated dibenzodioxins and furans were found in the combustion gases from all room tests. No brominated dioxins were found, however brominated furans were found. Further, the results from the room tests indicate that a TV-set treated with brominated flame retardants included in the fire load of a room fire does not necessarily increase the emission of bromine containing organic combustion products. The methodology applied for the sampling and analysis has been described in Part I of this series of articles.     

Fire detection, location and heat release rate through inverse problem solution. Part I: Theory

A proposed method of detecting, locating and sizing accidental fires, based on the solution of an inverse heat transfer problem, is described. The inverse heat transfer problem to be solved is that of the convective heating of a compartment ceiling by the hot plume of combustion gases rising from an accidental fire. The inverse problem solution algorithm employs transient temperature data gathered at the ceiling of the compartment to determine the location and heat release rate of the fire. An evaluation of the proposed fire detection system, demonstrating the limits on the accuracy of the inverse problem solution algorithm, is presented. The evaluation involves operating the inverse problem solution algorithm on transient temperature data from computer simulated compartment fires. The simulated fire data are generated assuming fires with quadratic growth rates, burning in a 20 m wide by 20 m deep by 3 m high enclosure with a smooth, adiabatic ceiling. The accuracy of the inverse problem solution algorithm in determining the location of a fire is shown to be insensitive to the errors in the fire model used in the forward problem solution, but sensitive to errors in the measured temperature data. The accuracy of the heat release rate of the fire is sensitive to both errors in the fire model and errors in the temperature data. The validity of the use of computer simulated data in the evaluation is verified with a second evaluation using fire data interpolated from published measurements taken in large-scale compartment fire burns.     

A combined overall and surface energy balance for fully-developed ventilation-controlled liquid fuel fires in compartments

As part of the research to extend the understanding of fully-developed wood fires to non-cellulosic fuels, the outline of a theoretical energy balance for a liquid fuel fire in a compartment is presented. A computer solution of the heat balance is described and the results of simulated fires are given to illustrate the uses of the model and the limitations of the assumptions made in the theory.The results show systematic departures from the well known assumption of the constancy of the ratio of burning rate to ventilation rate; this can account for some of the scatter commonly found in measurements of this ratio.     

更正说明

室内火灾具有较高的危险性,是建筑火灾造成人员伤亡和财产重大损失的灾害之首。利用计算流体动力学(CFD)的方法,建立了室内火灾时期烟气流动的三维大涡数值模型,目的是通过对火灾烟气流动的数值模拟,为多室火灾的控制和人员救助提供理论基础。模拟结果认为,火灾及附近地区温度较高,烟流浓度较大,高温引燃其他易燃物品的可能性加大。通风与火灾的发展状态存在密切关系,通风既能降低室内温度,加快烟流及有毒有害气体的扩散速度,同时也为火灾的进一步发展提供条件。从模拟结果与实验验证可得出结论:火源功率大小及房屋的几何尺寸影响着火灾程度、温度及烟流浓度的分布和变化,数值计算的结果总体上与实测结果存在较好的一致性。     

Correlation of autopsy data and materials involved in the Tennessee jail fire

During 1977, a number of major fires, resulting in multiple fatalities, have caused an enhanced concern about toxic gases that are generated from synthetic materials involved in the fire. One of these fires, the Maury County, Tennessee, jail fire, was unique in that the cell padding was the only material involved in the fire. Various officials from the State of Tennessee provided material samples for polymer identification and biological samples from victims for toxicological evaluation. The results of these measurements are presented. A correlation of the toxicological findings with the material involved in the fire is presented.     

Full scale fire tests for ship accommodation quarters

Ten full-scale test fires were conducted in a chamber simulating a three person ship accommodation quarter. The test fires used three different ventilation conditions, two types of bunks and furnishings with either polyurethane foam or chloroprene foam. The chamber was instrumented to follow the development of the fire.The furnishings with polyurethane foam were readily ignited and produced an intense fire within 2 to 4 minutes. The furnishings with chloroprene foam ignited but burned slowly with a small flame or in smoldering combustion.The ventilation conditions had a significant effect on the development and intensity of the fire as the test fires were burning under oxygen-limiting conditions.The solid pan bunks retarded the early development of the fire compared to open bunks for polyurethane furnishings. However, once the mattresses on the three bunks were ignited the intensity of the test fires was similar for both types of bunks.     

The critical ventilation velocity in tunnel fires—a computer simulation

In ventilated tunnel fires, smoke and hot combustion products may form a layer near the ceiling and flow in the direction opposite to the ventilation stream. The existence of this reverse stratified flow has an important bearing on fire fighting and evacuation of underground mine roadways, tunnels and building corridors. In the present study, conducted by the National Institute for Occupational Safety and Health, a CFD program (fire dynamics simulator) based on large eddy simulations (LES) is used to model floor-level fires in a ventilated tunnel. Specifically, the critical ventilation velocity that is just sufficient to prevent the formation of a reverse stratified layer is simulated for two tunnels of different size. The computer code is verified by checking the computed velocity profile against experimental measurements. The CFD results show the leveling-off of the critical ventilation velocity as the heat release rate surpasses a certain value. At this critical ventilation, the ceiling temperature above the fire reaches a maximum for both tunnels. The velocity leveling-off can be explained from this observation. An extended correlation of Newman (Combust. Flame 57 (1984) 33) is applied to the temperature profiles obtained by CFD. At the critical ventilation, temperature stratification exists downstream from the fire. The computed critical ventilation velocity shows fair agreement with available experimental data taken from both horizontal and inclined fire tunnels. The CFD simulations indicate that the Froude modeling is an approximation for tunnel fires. The Froude-scaling law does not apply to two geometrically similar fire tunnels. The CFD results are compared with two simple theories of critical ventilation by Kennedy et al. (ASHRAE Trans. Res. 102(2) (1996) 40) and Kunsch (Fire safety J. 37 (2002) 67).     

The effects of simulated fire pressure and outside wind on the internal pressure distribution in a five-storey model building

This paper presents some of the wind tunnel pressure measurements made on a five-storey model building (32 cells), with a vertical shaft and fixed leakage characteristics. Internal and external pressures measurements are presented for various wind angles and a simulated fire pressure in a room on floor 2 and floor 4. Comparison is made to assess the effect of fire on internal pressure distribution. Although the results are presented for all the wind angles investigated, a detailed discussion is confined only to a single wind angle. Implications of the combined effect of wind and fire on the shaft pressurization system design calculations must take these two factors into account.

In a fire situation it is possible that escapers may leave some of the shaft doors open or the fire room door may burn down. In such a case the pressurization system can become ineffective, causing escape routes to get smoke-logged. The effect of a combination of fire door openings was also investigated. The results for the following door opening combinations are presented and discussed:

1. (i) shaft door open alone;

2. (ii) fire room door open alone;

3. (iii) shaft and fire room doors open together.

It is shown quite clearly that these openings are significant for a range of wind angles.     

Fire detection using time series analysis of source temperatures

The evaluation of a near-infrared fire detector using standard test fires is presented. The spectral radiation intensities incident on the fire detector are continuously measured at two near-infrared wavelengths (900 and 1000 nm), and a time series of apparent source temperatures is obtained from these measurements. The power spectral density and the probability density function of the apparent source temperatures are sufficient to determine the presence of a fire in the vicinity of the detector. The detector can also indicate the presence of a fire in an adjoining room from the radiation which is incident on it due to reflections from common building materials.     

Estimating the Flashover Probability of Residential Fires Using Monte Carlo Simulations of the MQH Correlation

An important indicator of fire hazard in residential fires is the occurrence of flashover in the room of fire origin. Since the variability of residential fire scenarios is large, many different cases must be considered to evaluate the hazard of a given flammable product. Efficiently predicting the occurrence of flashover of a naturally ventilated compartment is possible using the correlation of McCaffrey, Quintiere, and Harkleroad (MQH). The large variability in United States (U.S.) living room fire scenarios is characterized from available data and propagated through the MQH correlation using Monte Carlo (MC) simulation. For the parameters, for which no relevant data was found, uniform probability distributions were assumed. The scenarios sampled in the MC simulations generally fell within the range of scenarios for which the MQH correlation has been validated. Flashover probabilities were estimated for fires up to 5 MW in heat release rate (HRR) and up to 8 min in duration. It was found that fires with HRRs less than 400 kW have a flashover probability of less than 0.01% regardless of their duration. Typical furniture fires were used as example cases, and it was predicted that a three seat upholstered sofa with a peak HRR of 2.15 MW has a 90% chance of flashing over a randomly chosen U.S. living room. The results of a global sensitivity analysis indicates that the fire location parameter and the vent opening width are the most important parameters affecting the prediction of the occurrence of flashover in U.S. living rooms. The methodology presented is generalizable, and the results can be readily improved by the collection of more data and the use of higher fidelity fire models.     

A parametric natural fire model for the structural fire design of multi-storey buildings

A parametric natural fire model is presented, which is derived on the basis of simulations with heat balance models for realistic natural design fires, taking into account the boundary conditions of typical compartments in residential and office buildings. These so-called iBMB parametric fire curves are formulated with the help of simplified empirical equations which can easily be used for structural fire design as part of a performance-based natural fire design concept. The iBMB parametric fire curves are checked and validated by comparison with results of different heat balance models and with published fire tests from different fire research laboratories. In addition, a natural fire test in a test room with ordinary office room furnishings has been performed which supports the parametric natural fire model presented here. The application of the iBMB parametric fire curves is demonstrated by means of an example.     

非均匀火灾作用下方钢管混凝土柱受力机理研究

对单面、相对两面、三面及四面火灾作用下方钢管混凝土柱截面的典型温度场及其分布规律进行分析,研究方钢管混凝土柱轴向/侧向变形-时间关系曲线,得到不同受火条件对方钢管混凝土柱抗火性能的影响规律。结果表明,相对两面和四面受火的柱截面温度场双轴对称,因而截面材料强度场、温度应变、温度应力也呈双轴对称分布,柱受力机理与常温情况下类似;对于单面和三面受火情况,由于柱截面温度场单轴对称,使得柱受力模式与常温情况不同,受火过程中柱先弯向受火侧,然后弯向背火侧。与温度梯度产生的非均匀的温度变形和材料强度偏心相比,受火面的多少在更大程度上决定了试件的抗火性能,即在绝大多数情况下,四面受火、三面受火、相对两面受火及单面受火的方钢管混凝土柱的耐火极限依次增大。但在某些特殊情况（如长细比λ<30）下,三面受火的方钢管混凝土柱的耐火极限可能小于其四面受火情况,此时如按四面受火对方钢管混凝土柱进行抗火设计,将存在安全隐患。     

The Influence of Tunnel Geometry and Ventilation on the Heat Release Rate of a Fire

It has occasionally been observed that fires in tunnels appear to be significantly more severe than fires in the open air. A literature review has been carried out, comparing heat release data from fires in tunnels with heat release data from similar fires in the open air. A Bayesian methodology has been used to investigate the geometrical factors that have the greatest influence on heat release rate. It is shown that the heat release rate of a fire in a tunnel is influenced primarily by the width of a tunnel; a fire will tend to have a higher heat release rate in a narrow tunnel rather than in a wide tunnel. The observed relationship between heat release rate and tunnel width is presented. Results from a study investigating the variation of heat release rate with ventilation velocity for fires in tunnels are also presented. A method for making realistic estimates of the heat release rates of fires in tunnels, based on these results, is presented.     

The burning of large pool fires

A non-intrusive method for obtaining the spatial distributions of radiative properties (i.e.) absorption-emission coefficients and radiation temperatures) in pool fires is described. The method consists of measuring the lateral transmittance and radiance of the fire and performing an Abel inversion on the measurements to obtain absorption-emission coefficients and local radiation temperatures in the fire. Local radiative properties so obtained are used to calculate the flame radiation flux—the dominant heat transfer mode —to the pool surface. The computed flux is in good agreement with the flux inferred from experimentally measured burning rates of the fire. These experiments are performed on a 0.73 m diameter PMMA pool fire. The results presented here show that large pool fires tend to be significantly non-uniform in temperature and species concentrations and the non-uniformities play an important role in determining the burning rate of these fires.     

Flames venting externally during full-scale flashover fires: two sample ventilation cases

The effects of burn room ventilation and environmental conditions on venting plumes have been examined during a series of full-scale flashover fires at the Experimental Building Fire Facility of CESARE (Centre for Environmental Safety and Risk Engineering) of Victoria University of Technology. The focus in this paper is on two typical test cases, each corresponding to one of the two ventilation classes examined during this series of fires, namely, Class 1: through-draft (flow through) and Class 2: no-through-draft conditions. These conditions correspond to the open door and window in the burn room, and the closed door and open window, respectively. Three-dimensional temperature contours outside the burn room have been used to study plume dispersion. Total and radiant heat flux measurements, combined with the overall reach and severity of venting flames indicate that flames emerging from the room of fire origin are capable of initiating a secondary fire in the level above. While each fire has a natural periodicity innate to the combustion process itself, any swirling motion of the venting plume has been observed to be caused by a cross-wind.     

Comparison of different combustion models in enclosure fire simulation

In this study, three combustion models, the volumetric heat source (VHS) model, the eddy break-up model and the presumed probability density function (prePDF) model, are examined in enclosure fire simulation. The combustion models are compared and evaluated for their performance in predicting three typical enclosure fires, a room fire, a shopping mall fire and a tunnel fire. High Reynolds number turbulence k–ε model with buoyancy modification and the discrete transfer radiation model (DTRM) are used in the simulation. Corresponding experimental data from the literature are adopted for validation. The results show satisfactory prediction in flow patterns and features in the complex enclosure fires. However, it is shown that these combustion models are not able to show consistent performance over the different locations and enclosure fires. The needs for adequate turbulent combustion models in enclosure fires are discussed.     

A Risk-Based Method of Deriving Design Fires for Evacuation Safety in Buildings

This article presents a risk-based method for building fire safety design. Because the design fire is the most critical aspect of a building fire safety design, this article uses reliability theory to derive design fires from the fire risk acceptance criteria. The fire scenarios are modeled by an event tree, where different fire protection systems are presented as pivotal events. The number of casualties is estimated by the occupant number and the probability that an untenable condition is reached before occupants evacuate to a safe location. Using the probability and consequence of each fire scenario, the expected risk to life is used to integrate the fire risk acceptance criteria into the determination of the target reliability index. A global optimization method is then applied to the reliability index to obtain the design fires for each scenario. A case study was conducted to demonstrate an application of this proposed method.     

Variation of heat release rate with forced longitudinal ventilation for vehicle fires in tunnels

Many tunnels are equipped with longitudinal ventilation systems to control smoke in the event of a fire. However, the influence of such ventilation on fire development and fire spread has rarely been considered. This paper presents the results of a study using a Bayesian methodology to estimate the effect of forced longitudinal ventilation on heat release rate (HRR) for fires in tunnels. The behaviour of car and heavy goods vehicle (HGV) fires with a range of forced ventilation velocities is investigated. Results are presented and the implications are discussed. It has been found that forced ventilation has a great enhancing effect on the HRR of HGV fires, but has little effect on the HRR of car fires.     

Use of fire statistics in behavioural studies

This paper gives data on information available on casualty incidence and behaviour from fire brigade reports. The data presented appear to refute several popular beliefs about the typical casualty fire.Fire brigade data are large in volume and cover a wide range of fires but provide only limited information on each individual fire. Thus, for further information on behaviour patterns, some fires will have to be investigated in detail.