Fire Technology最新文献

Electric vehicle (EV) fire accidents have attracted widespread attention in recent years. Particularly, EV fires in underground parking garages may exhibit much higher hazards than those in open spaces owing to the limited space and poor ventilation. However, the fire evolution process and corresponding hazards of EVs parked in underground parking garages are still unclear. In this study, a gasoline in a square oil pan was used to ignite the chassis of EVs in the underground parking garages, and the fire evolution process and characteristics were investigated by analyzing the burning behaviors, temperature variations, thermal radiation, and smoke concentrations. The results show that the fire evolution of EVs adopting blade batteries as the energy source can be divided into three stages: EV body burning, the battery pack and vehicle body co-combustion, and combustion decline. The temperature spread rate of the chassis of EVs can reach 0.0141 s^− 1. According to the radiation model, the safe distance for unprotected personnel was 8.7 m. In addition, during the EV fire in underground parking garages, the major gases released mainly consist of CO₂, CO, NO, NO₂, NO_x, and SO₂, and asphyxiating gases are less hazardous than irritating gases. This work investigates the evolution and hazards of EV fires in confined spaces, and the results can provide scientific guidance and data for the layout and fire protection strategies of EVs in underground parking garages.

Lithium-ion battery fires present increasing safety engineering challenges, with U.S. incident rates rising 86% between 2020 and 2023, particularly in micromobility devices and urban environments. We analyzed 148 lithium-ion battery fire incidents documented through the Massachusetts State Fire Marshal’s specialized checklist program, employing logistic regression for charging-related risks, spatial clustering for geographic patterns, and time-series analysis for temporal trends. Consumer electronics showed significantly lower odds of charging-related fires (OR = 0.125–0.148, p < 0.05), while micromobility devices had the highest injury rate (IRR = 2.98, 95% CI: 0.837–10.615). Charging was involved in 40.5% of cases, and online purchases were associated with greater risk (OR = 1.87, 95% CI: 1.23–2.84, p = 0.003). Significant urban clustering was observed (Moran’s I = 0.28, p = 0.003) with three metropolitan hotspots. Device-specific risk profiles demonstrate the effectiveness of existing consumer electronics safety standards and highlight critical intervention points for emerging high-risk devices, particularly in dense urban areas where targeted protection strategies are most needed.

This paper describes the development and validation of a computational framework to examine the rate-dependent behavior of steel columns subjected to fire temperatures (400 °C to 1000 °C). A unique set of data from elevated-temperature tension and creep tests on samples of ASTM A992 steel along with data from elevated-temperature buckling tests on ASTM A992 steel columns were used in the validation process. The material and column experiments were conducted under steady-state temperature conditions. The objective of the computational study was to validate the adequacy of the computational modeling approach to predict the impact of loading rate on the buckling capacity of steel columns at elevated temperatures and to provide additional insights into the rate- and temperature-dependent behavior of steel columns exposed to the loading and temperature conditions expected in structurally significant fires. The computational model of the steel columns accounted for both geometric and material nonlinearities. Specifically, the thermal creep of steel was explicitly included in the material characterization of steel at elevated temperatures. The paper demonstrates the advantage of defining the deformation behavior of steel explicitly as a function of time in predicting the impact of loading rate on both material and column response to high temperatures. For example, the reduction of the loading rate from 2.50 mm/min to 0.05 mm/min at 700 °C resulted in the decrease in the yield stress and the ultimate stress of A992 steel by 45% and 35%, respectively. Lower loading rates also reduce the buckling capacity of A992 steel columns by 33% at 800 °C, with more pronounced effects at lower slenderness ratios. The potential shortcomings of the current code treatment of the influence of loading rate on steel column capacity at elevated temperatures are further discussed.

The reliability of photoelectric-type smoke detectors, widely employed for early fire detection in buildings, is often compromised due to frequent false alarms triggered by nuisance aerosols. While multi-sensor detectors offer improved discrimination, their implementation remains limited. To overcome these issues, the present study investigates the light scattering characteristics of smoke particles and nuisance aerosols using a light-scattering chamber (LSC) specifically designed to retain the simplicity of conventional photoelectric-type smoke detectors. The LSC features a single light source and multiple photodetectors strategically positioned at 12 uniformly distributed angles to capture scattering phenomena. The analysis revealed distinct scattering behaviors between smoke particles and nuisance aerosols. Specifically, smoke particles predominantly produce backward scattering, where light is scattered opposite to the propagation direction. In contrast, nuisance aerosols exhibit pronounced forward scattering. This difference can be attributed to particle size–dependent differences in light absorption and transmission. From a practical standpoint, it was demonstrated that using only two photodetectors positioned to capture forward and backward scattering angles is sufficient to effectively distinguish between particle types. This finding suggests that conventional photoelectric-type smoke detectors can achieve significantly enhanced particle differentiation capabilities with a simple structural modification that incorporates an additional photodetector. This approach holds substantial promise for improving the reliability and performance of fire detection systems while maintaining their cost-effectiveness and simplicity.

Engineered cementitious composite (ECC)-encased concrete filled steel tube (CFST) columns represent an innovative composite member that synergistically harnesses the advantages of ECC and CFST, exhibiting superior load-bearing capacity and ductility compared to existing concrete-encased CFST columns. Building on previous research, this study investigates the post-fire eccentric loading behavior of ECC-encased CFST columns based on heat transfer theory and finite element (FE) theory. Initially, constitutive models considering temperature parameters for different materials (ECC, concrete, and steel) were proposed, subsequently establishing a temperature field analysis model for ECC-encased CFST columns under the effects of heating and cooling during a fire. Mechanical performance analysis models were then developed to assess the behavior of ECC-encased CFST columns under normal temperature and post-fire conditions. The reliability of the FE models was verified, with a particular focus on the eccentric loading failure mechanism of ECC-encased CFST columns after a fire. Furthermore, based on the proposed FE models, a comprehensive parametric analysis was conducted to investigate the eccentric loading performance of the composite columns in the post-fire scenario. The paper focuses on the numerical study and parametric analyses ECC-encased CFST columns exposed to fire, contributing to the enhancement of structural safety in fire-prone environments.

Experiments on equal and unequal double rectangular pool fire of aviation kerosene (RP-5) were carried out in the wind speed range of 0–8.0 m/s. The results indicate that the flame merging state can be divided into three stages: fully merging, intermittent merging, and non-merging. Flame merging probability decreases with increasing pool spacing. The decreasing tendency of flame merging probability slows down in the wind environment. The merging probability is greater for unequal conditions than equal ones at the same pool spacing due to the larger pool size. Meanwhile, a predictive formula for the merging probability varying with S/L_{S, V} has been proposed. The burning rate generally increases with the growth of wind speed. The equivalent side length parameter D* is proposed based on pool size and pool spacing. The total burning rate is the sum of the burning rates of the two pools. Dimensionless treatment of the per unit area burning rate (({dot{m}}^{prime prime}_{total,V}/{dot{m}}^{prime prime}_{total,0})) under still air was performed. A linear formula for the dimensionless per unit area burning rate versus Fr* is presented. Under windy conditions, flames are tilted downwind, but the tilt angle of the downwind flames is reduced compared to the upwind flames as a result of the sheltering effect. The unequal pool condition demonstrates a greater sheltering effect on the downwind pool. Flame length increases and then decreases with growing wind speed. The flame length reaches its maximum at a wind speed of 6.0 m/s, but at higher wind speeds, vapors are blown away before ignition, leading to a shorter flame length. The burning rate correlation coefficient (({dot{m}}^{prime prime}_{total,0}/{dot{m}}^{prime prime}_{total})) is introduced to eliminate the influence of oil pool size. An exponential relationship between dimensionless flame length (L_f /D*) and dimensionless heat release rate (({dot{Q}}^{ast} cdot {dot{m}}^{prime}_{coe})) was found and a prediction formula was proposed.

This study analyzes the results of more than 100 CFD simulations of smoke spreading in a double-deck tunnel with a branch duct exhaust system. A single fire source is positioned in the lower deck of the tunnel, flush with the floor and in the center between the side walls. The CFD study provides detailed flow information which could not be measured in the experiments reported in earlier work (Wang et al. in Fire Saf J 146:104144, 2024, https://doi.org/10.1016/j.fi​resaf.2024.104144), hence the CFD study provides very useful complementary information, which allows for better understanding of the observed phenomena. The following parameters are varied: fire heat release rate (HRR); smoke extraction flow rate; and the number of vents, as well as their location, opened in the lower deck (and leading to the branch ducts). The impact of leakage is discussed as well. The results reveal that: (i) the smoke spreading distance (SSD) increases with HRR as the ceiling jet strengthens, but once smoke/heat escapes through a tunnel portal, the effective HRR inside the tunnel drops and the opposite-side SSD shortens; (ii) leakage significantly reduces flow velocities and enlarges SSD, quantifying the sensitivity of smoke control effectiveness to sealing quality; and (iii) with symmetric openings around the fire and one-sided extraction, the ratio of downstream SSD to the total SSD is approximately proportional to the ratio of upstream to total air inflow volume flow rate, providing a predictive indicator for vent performance. Applicability bounds and long-tunnel usage are stated to guide design and operations.

Lithium battery fires can lead to severe casualties and significant property losses. Proactively evaluating and predicting lithium battery hazards enables timely preventive measures, thereby mitigating the severity of potential fire incidents through enhanced safety management. Therefore, conducting risk assessments and implementing safety measures for lithium battery fires is essential. Firstly, this study classified lithium battery fire risks into four grades and summarized the key factors contributing to battery fires. Secondly, it developed an integrated Fuzzy Bayesian Network (FBN) model that innovatively combines fishbone diagram analysis with probabilistic reasoning to quantitatively assess the complex interdependencies among fire-inducing factors. To validate the model’s effectiveness, a case study was conducted, and the results align with the actual risk levels of historical accidents, confirming the model’s reliability. This model can serve as a valuable reference for lithium battery fire risk evaluation. Furthermore, based on the case study findings and the constructed risk assessment model, a corresponding safety management system was established. This system helps reduce accident occurrence and minimize the severity of their consequences.

The fire may break out anywhere in a long tunnel using point extraction ventilation; however, the role of longitudinal fire position between two dampers on smoke propagation and control is unknown. Therefore, the effect of longitudinal fire position between two dampers on smoke propagation and control was investigated, considering different heat release rates (HRRs) and damper sizes. The ceiling temperature, the velocity field on both sides of the fire, and the mass flow rate of the smoke and air were analyzed. The results demonstrated that the velocity field on both sides of the fire became asymmetric, and the flame inclination appeared when the fire deviated from the middle between the two dampers under a low exhaust rate. Interestingly, the velocity field on both sides of the fire actually became quasi-symmetric, and the flame hardly tilted when the exhaust rate rose to a certain value. This was attributed to the reallocate of the mass flow rate of smoke and fresh air based on the two-layer model. Besides, the ceiling temperature profile was not sensitive to the longitudinal fire position when the exhaust rate increased to a certain value. Finally, a formula was developed to predict the required exhaust rate for removing all smoke through two dampers, considering a fire occurring anywhere in a tunnel. These findings hope to provide helpful references for tunnel ventilation engineers.

Underground coal fires (UCFs) have caused disasters in most coal-producing countries, and their dominant burning mode is smouldering combustion which is controlled by oxygen supply. Cracks and fissures in the overlying layer(s) provide air (oxygen) to sustain the smouldering propagation underneath. The effects of multiple cracks’ spacings and their distribution on smouldering characteristics have not been addressed in the literature. With some reasonable simplifications and assumptions, a lab-scale experimental setup comprising a packed coal bed and an overlying layer with multiple cracks was constructed to fill the research gap. Three experimental cases were designed to investigate the effects of cracks’ spacings in order to identify the limiting conditions. The coal bed temperature and gaseous emissions were measured, based on which it was found that the limiting crack spacing (L_c) for self-sustained smouldering propagation is about 6 mm. It is interesting to observe that the propagation was not in a sequential manner, that is, positions further from the ignition source might enter the smouldering mode earlier under proper thermal (temperature) and chemical (oxygen content) conditions. The cracks played an important role in determining the smouldering intensity underneath, depending on two main properties of each crack, they are, its spacing and oxygen concentration in it.