Search Results (12)

The vast majority of fire-related deaths occur in residential buildings. Until recently, the fire risk for these buildings was only considered through static risk assessments or period-based assessments applying to certain periods of the year, e.g., Christmas holidays. However, for homes with indoor wooden panelling, especially in the ceiling, a dynamic fire danger indicator can be predicted for cold climate regions. Recognising the effect of fuel moisture content (FMC) of indoor wooden panelling on the enclosure fire development allows for the prediction of a wooden home fire danger indicator. In the present study, dry wood fire dynamics are analysed and experimental observations are reported to support in-home wooden panel FMC as a suitable wooden home fire danger indicator. Then, from previous work, the main equation for modelling in-home FMC is considered and a generic enclosure for FMC modelling is justified based on literature data and supported through a sensitivity study for Norwegian wooden homes. Further, ten years of weather data for three selected locations in Norway, i.e., a coastal town, an inland fjord town and a mountain town, were analysed using a three-dimensional risk matrix to assess the usability of the fire risk modelling results. Finally, a cold climate wooden home fire danger index was introduced to demonstrate how the risk concept can be communicated in an intuitive way using similar gradings as the existing national forest fire index. Based on the generic enclosure, the findings support FMC as a fire risk indicator for homes with interior wooden panelling (walls and ceiling). Large differences in the number of days with arid in-home conditions were identified for the selected towns. The number of days with combined strong wind and dry wooden homes appears to depend more on the number of days with strong wind than days of in-home drought. Thus, the coastal town was more susceptible to conflagrations than the drier inland towns. This aligns well with the most significant fire disasters in Norway since 1900. In addition, it was demonstrated that the number of high-risk periods is manageable and can be addressed by local fire departments through proactive measures. In turn, the fire risk modelling and associated index respond well to the recent changes in Norwegian regulations, requiring the fire departments to have systems for detecting increased risk levels. Testing the modelling for a severe winter fire in the USA indicates that the presented approach may be of value elsewhere as well. Full article

The fire scenarios currently used for structural fire design are based on traditional methods that derive from the extrapolation of existing fire test data. The traditional “furnace” geometry test allows a good circulation of the fire gases and a relatively homogeneous temperature distribution throughout the enclosure. These conditions are different from what is observed in real-situation fires. As a result, the need for a field model for an enclosure fire has increased significantly, and appropriate deterministic models are necessary for fire safety engineering. The effects of different strategies involving the opening of doors and windows with changes in the enclosure’s geometry were observed to gain an insight into the impact of how ventilation and geometry influence changes during the development of a fire. This article presents and discusses the results of the field model compared with similar tests and experiments described in the technical and scientific literature. Generating data using a field model reduces experimental costs and facilitates sensitivity analyses of the parameters of problems. Full article

This article presents a numerical analysis of the performance of three water mist fire suppression systems, with different characteristics, on shielded fires as representing more realistic fire scenarios in an enclosure. A diesel pool fire with a peak heat release rate (HRR) value of 75 kW is covered by an obstacle above it with different shielding conditions to investigate the influence of the obstacle size and the vertical distance between the obstacle and the nozzle on the efficiency of the water mist systems. The obstacle prevents a large number of droplets from directly reaching the fuel surface and flames. The modeling and numerical analysis of this study were carried out by the fire dynamics simulator (FDS) programming tool, and the designed model was validated against the experimental data for both dry and wet tests. The results show that two of the analyzed mist sprays could successfully extinguish the shielded fires in a short time with an obstacle size of 25 cm × 25 cm and 50 cm × 50 cm, placed at two heights. However, the third mist system had a longer extinguishing time compared to the first two nozzles. All three nozzles failed to suppress the fire covered by the largest obstacle (1 m × 1 m). The shielding conditions and nozzle characteristics can affect the performance of water mist systems to some extent. Full article

Fire disasters in informal settlements (also referred to as slums, shantytowns, favelas, etc.) are a major challenge worldwide, with a single incident being able to displace thousands of people. Numerous factors including dwelling spacing, material type, topography, weather, fuel loads, roads, and more influence fire spread. Conducting large-scale experiments to quantify and understand these phenomena is difficult and costly. Hence, it would be beneficial if Reduced Scale Experiments (RSE) could be developed to study the influence of these phenomena. Previous research has demonstrated that a 1/4th scale informal settlement dwelling (ISD) RSE can sufficiently capture the fire behaviour and fire dynamics within dwellings. The objective of this work is to develop a methodology for multi-dwelling ISD scaling such that large-scale spread phenomena can be captured. This paper carries out a series of RSEs to study the influence of (a) the number of dwellings, (b) orientation of dwellings, windows, and door openings, (c) cladding material, (d) wind effects, (e) the distance between dwellings and (f) fuel load on spread. Results are compared to previous large-scale experiments. It is shown that the geometric scaling of distance between dwellings is suitable for capturing spread. It was found that wind and the fuel load contribute significantly to the fire spread, but the type of cladding, distance between dwellings, dwelling orientation, and type of structural members used also affects fire spread rates. The comparative results with full-scale experiments (FSEs) shows that the peak temperatures were comparable and had similar profiles. A good correlation exists between FSEs and RSEs in terms of fire dynamics and spread characteristics, but the spread time (scaled or unscaled) does not correlate well with FSEs. Further work is needed before the work can be reliably used for predicting multi-dwelling spread, especially when wind is involved, due to the complex interaction of parameters and difficulty in scaling flame impingement. Full article

Numerical investigations have been carried out for a postulated enclosure fire scenario instigated due to methanol pool ignition in a chemical cleaning facility. The pool fire under consideration is radiation-dominated and poses a risk to the nearby objects if appropriate safety requirements are not met. The objective of the current study was to numerically evaluate the postulated fire scenario and provide safety recommendations to prevent/minimize the hazard. To do this, the fire scenario was first modeled using the finite volume method (FVM) based solver to predict the fire characteristics and the resulting changes inside the enclosure. The FDS predicted temperatures were then used as input boundary conditions to conduct a three-dimensional heat transfer analysis using the finite element method (FEM). The coupled FVM–FEM simulation approach enabled detailed three-dimensional conjugate heat transfer analysis. The proposed FVM–FEM coupled approach to analyze the fire dynamics and heat transfer will be helpful to safety engineers in carrying out a more robust and reliable fire risk assessment. Full article

To protect the personnel of the intervention units operating in high-risk areas, it is necessary to introduce (autonomous/semi-autonomous) robotic intervention systems. Previous studies have shown that robotic intervention systems should be as versatile as possible. Here, we focused on the idea of a robotic system composed of two vectors: a carrier vector and an operational vector. The proposed system particularly relates to the carrier vector. A simple analytical model was developed to enable the entire robotic assembly to be autonomous. To validate the analytical-numerical model regarding the kinematics and dynamics of the carrier vector, two of the following applications are presented: intervention for extinguishing a fire and performing measurements for monitoring gamma radiation in a public enclosure. The results show that the chosen carrier vector solution, i.e., the ground vehicle with six-wheel drive, satisfies the requirements related to the mobility of the robotic intervention system. In addition, the conclusions present the elements of the kinematics and dynamics of the robot. Full article

Recent explosions with devastating consequences have re-emphasized the relevance of fire safety and explosion research. From earlier works, the severity of the explosion has been said to depend on various factors such as the ignition location, type of a combustible mixture, enclosure configuration, and equivalence ratio. Explosion venting has been proposed as a safety measure in curbing explosion impact, and the design of safety vent requires a deep understanding of the explosion phenomenon. To address this, the Explosion Venting Analyzer (EVA)—a mathematical model predicting the maximum overpressure and characterizing the explosion in an enclosure—has been recently developed and coded (Process Saf. Environ. Prot. 99 (2016) 167). The present work is devoted to methane explosions because the natural gas—a common fossil fuel used for various domestic, commercial, and industrial purposes—has methane as its major constituent. Specifically, the dynamics of methane-air explosion in vented cylindrical enclosures is scrutinized, computationally and experimentally, such that the accuracy of the EVA predictions is validated by the experiments, with the Cantera package integrated into the EVA to identify the flame speeds. The EVA results for the rear-ignited vented methane-air explosion show good agreement with the experimental results. Full article

Inert gas agents have the potential to be widely used in fire suppression systems due to health and safety concerns associated with active chemicals. To suppress fire while minimizing hypoxic effects in an occupied area, the discharge quantity of inert gas agents should be carefully designed to dilute the oxygen concentration to a specific threshold level. In this study, the general expressions between oxygen concentration, the discharge rate of inert gas agents, and the ventilation rate of the air-agent mixture are derived first. Then, explicit formulas to calculate the discharge/ventilation rate and the required quantity of inert gas agents are given if the discharge rate and ventilation rate both are constants. To investigate the dilution and fire extinguishing efficiencies of inert gas agents, two scenarios with a discharge of inert gas agents into an enclosure are modeled using the Fire Dynamic Simulator (FDS). The simulation results show that the average oxygen mass fraction approximately reaches the design level at the end of the discharge period. Variation in oxygen concentration along the enclosure height is analyzed. For the scenario with a fire source, oxygen mass fraction decreases fast as oxygen is consumed by the combustion process. Thus, the fire is extinguished a little earlier than the end of the discharge period. Full article

Alternative and innovative fuel types are being introduced to power cars. These include liquified petroleum gas (LPG) gas and hydrogen energy sources. However, they also introduce new hazards, requiring revised thinking with respect to safety within car parking environments. One of the most significant dangers is accidental gas release from a car’s system, especially in underground car parks. Jet fan systems are widely used for ventilation of such enclosures, but currently their design is most often based on computational fluid dynamics (CFD) according to computer simulations that may not be relevant for such new fuels. This paper presents the results of full-scale tests which demonstrate the operational factors of jet fan ventilation systems, and assesses the conditions which can occur in a car park when a small volume of LPG is released. On the basis of measurements undertaken, Fire Dynamics Simulator (FDS) software was validated against the air velocity flows and LPG gas dispersion patterns. Finally, the simulations were used to demonstrate the effectiveness of systems in an actual car park, in the case of an accidental LPG car tank release. Full article

When charging most types of industrial lead-acid batteries, hydrogen gas is emitted. A large number of batteries, especially in relatively small areas/enclosures, and in the absence of an adequate ventilation system, may create an explosion hazard. This paper describes full scale tests, which demonstrate conditions that can occur in a battery room in the event of a ventilation system breakdown. Over the course of the tests, full scale hydrogen emission experiments were performed to study emission time and flammable cloud formation according to the assumed emission velocity. On this basis, the characteristics of dispersion of hydrogen in the battery room were obtained. The CFD model Fire Dynamic Simulator created by National Institute of Standards and Technology (NIST) was used for confirmation that the lack of ventilation in a battery room can be the cause of an explosive atmosphere developing, and leading to, a potential huge explosive hazard. It was demonstrated that different ventilation systems provide battery rooms with varying efficiencies of hydrogen removal. The most effective type appeared to be natural ventilation, which proved more effective than mechanical means. Full article

Pressure differential systems have the purpose of maintaining tenable conditions in protected spaces for different types of building safe places, like escape routes, firefighting access routes, lobbies, stairwells and refuge areas. The aim of pressure differential systems is to establish airflow paths from protected spaces at high pressure to spaces at lower or ambient pressure, preventing the spread of toxic gas released during a fire. This strategy ought to be supported by a detailed design of the necessary air supply, considering also the cycle of opening and closing doors during the egress phase. The paper deals with the design of a simple pressure differential system intended to be used in a building as a pressurized smokeproof enclosure. Specifically, experimental tests and numerical modelling are conducted with the objective of characterizing the pressure evolution in a small compartment under different conditions and through a cycle of door opening. Experimental tests are conducted in a simple 3-m side cubic enclosure with two doors and no vent openings. While a centrifugal fan blows constant airflow inside the structure, the pressure trend in time is recorded during steady state and transient conditions; additionally, the velocity of the airflow across the doors has been measured by means of an anemometer. Numerical CFD (computational fluid dynamics) simulations are carried out to reproduce the same smokeproof enclosure configuration (both geometrical and boundary conditions) using the fire dynamics simulator (FDS). Furthermore, specific attention is paid to the modelling of the leakage across the doors, directly inserted in the model through a localized HVAC (heating and venting air conditioning) advanced leakage function. Comparisons between experimental tests and numerical simulations are provided. Once the model was correctly calibrated, other geometrical and mechanical configurations have been studied, looking for convenient and efficient positions of the fan in order to fulfill the requirements of the pressure differential, airflow velocity and door handle force. The paper highlights some fundamental aspects on the pressurization and depressurization during steady state and transient phases, trying to identify if there are airflow profiles typical of some geometrical configurations. Full article

With the Government of China’s proposed Energy Efficiency Regulations (GB40411-2007), the implementation of external insulation systems will be mandatory in China. The frequent external insulation system fires cause huge numbers of casualties and extensive property damage and have rapidly become a new hot issue in construction evacuation safety in China. This study attempts to reconstruct an actual fire scene and propose a quantitative risk assessment method for upward insulation system fires using thermal analysis tests and large eddy simulations (using the Fire Dynamics Simulator (FDS) software). Firstly, the pyrolysis and combustion characteristics of Extruded polystyrene board (XPS panel), such as ignition temperature, combustion heat, limiting oxygen index, thermogravimetric analysis and thermal radiation analysis were studied experimentally. Based on these experimental data, large eddy simulation was then applied to reconstruct insulation system fires. The results show that upward insulation system fires could be accurately reconstructed by using thermal analysis test and large eddy simulation. The spread of insulation material system fires in the vertical direction is faster than that in the horizontal direction. Moreover, we also find that there is a possibility of flashover in enclosures caused by insulation system fires as the smoke temperature exceeds 600 °C. The simulation methods and experimental results obtained in this paper could provide valuable references for fire evacuation, hazard assessment and fire resistant construction design studies. Full article