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15 April 2026, Volume 45 Issue 4 Previous Issue   

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Experimental study on combustion behavior of wood with longitudinal cracks at different angles Gu Heng, Peng Wei, Wang Yiting, Zhou Yue 2026, 45 (4):  1-6.  Abstract ( 79 )   Wood undergoes internal moisture loss due to weathering, leading to cracking most commonly longitudinal cracking. When such cracks extend deep into the heartwood, they significantly influence the wood's combustion behavior. Current research on timber structure buildings primarily focuses on moving away heat source after ignition and self-sustained combustion observations. In this experiment, wood samples with longitudinal cracks of 15 cm in length and varying cross-sectional depths of 4, 5, 6 cm were tested under different inclination angles, all under continuous external flame exposure. The results indicate that when the inclination angle reaches 30°, the combustion behavior changes markedly, with notable increases in temperature, mass loss, and charring length. The influence of longitudinal cracks on wood components manifests mainly in two aspects: first, by altering gas flow direction and increasing oxygen supply to the combustion zone; and second, by modifying heat transfer patterns. Cracks facilitate faster heat transfer from the alcohol flame into the wood interior, accelerate air flow along the cracks, and enhance convective heat effects. Related Articles | Metrics

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Experimental study on fire resistance of glued laminated timber floor slabs in timber hybrid structures Yang Zhiwei, Zhai Jiajun, Zhang Yongwang, Cheng Xiaowu 2026, 45 (4):  7-11.  Abstract ( 49 )   To ensure the fire safety of timber hybrid structures, a full-scale fire resistance test was conducted on horizontally bonded laminated timber (HBLT) floor slabs following the standard fire heating curve. The test results showed that the fire resistance rating of the HBLT floor slab was not less than 1.50 h. No collapse occurred to the test specimen after fire exposure, with a maximum mid-span deflection of 7 mm, indicating no loss of load-bearing capacity; no flame appeared on the unexposed surface, maintaining the integrity of the specimen; the average temperature of the unexposed surface rose by 26 ℃, and the maximum temperature at a certain point on the unexposed surface increased by 68 ℃, showing no loss of thermal insulation performance. In addition, the measured char layer thickness of the HBLT floor slab was within the design safety range. The above results demonstrate that the HBLT floor slab has excellent fire resistance under fire conditions, providing experimental evidence for the fire protection design of timber hybrid structures. Related Articles | Metrics

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Study on the development and spread of fire in Chuandou-style timber houses based on model test Zeng Fanjun, Zhou Li, Huang Yong, Tang Honggang 2026, 45 (4):  12-19.  Abstract ( 47 )   A full-scale experimental model of a Chuandou-style timber house was constructed to investigate the fire spread process, structural damage, and temperature variation characteristics through on-site fire tests. The test results indicated that the fire spread characteristics in each room were similar, starting with the accumulation of pyrolysis gases, followed by a flashover, and finally, the fire weakened as the fuel was consumed. The upper structural components burned before the lower ones, and the smaller the cross-sectional size of the components, the more severe the burning. Before the flashover in the room, the temperature in the upper space was higher, but the destruction of components such as windows and walls led to a large influx of cold air, causing the temperature in the upper space to drop rapidly. In addition, thermal imaging analysis revealed that the gaps in the attic floor and the seams of the wall panels are channels for the escape of pyrolysis gases, which tend to accumulate in the attic space. Related Articles | Metrics

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Research on key technologies for fire protection planning and design of ancient building complex Wang Jingbo, Li Songhan, Zheng Changyue, Zhao Jiaming 2026, 45 (4):  20-26.  Abstract ( 52 )   In view of the technical difficulties of ancient building complexes in China, such as the unsystematic top-level design of the fire protection system and the lack of relevant fire protection design standards in planning and design, this paper conducts in-depth research on the fire spread law through numerical simulation based on the investigation of fire loads in more than 20 brick-wood structure ancient building courtyards. Combined with actual combat drills, according to the principle of 3 min fire fighting and rescue coverage, a method for dividing fire protection responsibility areas in large ancient building complexes is proposed. Finally, a three-level alarm architecture planning and design method for the fire alarm system of large ancient building complexes is proposed from three aspects: the planning and design concept of the fire alarm system, the design requirements of centers at all levels, and the selection of fire detectors. Related Articles | Metrics

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Machine-learning-based hazard assessment of fire-inducing factors in ancient timber covered bridges Liu Jie, Wei Shilin, Pan Boyu 2026, 45 (4):  27-34.  Abstract ( 59 )   This study aims to quantitatively identify the relative hazard of different fire-inducing factors and to establish a metric framework applicable to large-scale screening and graded fire-risk management. Multi-source data including local gazetteers, official fire investigation reports, news records, and field surveys were integrated to construct a positive and negative sample database covering 226 ancient timber covered bridges and 285 disaster events. Fire occurrence (yes/no) was defined as the response variable, while eight fire-inducing factors—ritual fire use, fireworks setting off, electrical installations, combustible accumulation, tourism development, residential activities, lightning-prone areas, and important transportation nodes—were encoded as binary variables indicating presence or absence. Random Forest (RF), Support Vector Machine (SVM), XGBoost, and LightGBM classifiers were developed and compared, with model performance evaluated using accuracy (ACC) and the area under the ROC curve (AUC). The RF model exhibited the most balanced performance and was selected for subsequent analysis. Based on normalized feature importance derived from the RF model (MDI/Gini), hazard weights of fire-inducing factors were quantified, and a Fire-inducing Factor Hazard Index (FFHI) with a four-level classification scheme was further established. The results indicate that combustible accumulation (25.50%) and ritual fire use (21.20%) are the most hazardous factors, followed by residential activities (17.80%) and electrical installations (10.30%). Fireworks (8.30%) and important transportation nodes (8.20%) show comparable contributions, while tourism development (5.00%) and lightning-prone areas (3.70%) exhibit relatively lower weights. The FFHI ranges from 0 to 1 and enables rapid quantification of fire-inducing conditions at the individual bridge level, supporting classification into four hazard grades. The findings suggest that fire prevention for timber covered bridges should prioritize the control of combustible materials and ritual fire use, while simultaneously regulating residential activities and electrical installations. Context-dependent factors such as fireworks setting off, transportation nodes, and tourism peaks require strengthened time-specific management. The proposed FFHI and grading approach provide a quantitative basis for regional-scale screening, inspection prioritization, and intervention sequencing, and can be dynamically updated as new data become available. Related Articles | Metrics

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Study on the fire combustion characteristics and heat release of lithium iron phosphate battery electric bicycle Zhang Dianfei, Zhao Zhenghe, Meng Di, Li Haihang 2026, 45 (4):  35-42.  Abstract ( 48 )   Based on the ISO 9705 fire standard experiment, the thermal runaway of 48 V/20 Ah soft pack battery module was triggered by overcharging, and the voltage and surface temperature of the battery pack, the rate of heat release, the total amount of heat release and the flame temperature of the e-bike were measured and analysed. The results show that: the maximum surface temperature of the battery surface rises to 816.28 ℃, and the voltage of the battery plummets to nearly 0 V in about 600 s; the fire triggered by overcharging of the e-bike presents the form of spreading from the top to the bottom, and the maximum flame temperature is 848.8 ℃; the maximum heat release rate is 4 858.89 kW, and the total heat release amount is 1 219.03 MJ; The maximum heat release rate of the battery pack is about 4.54% of the maximum heat release rate of the whole vehicle, and the total heat release is about 8.40% of the total heat release of the whole vehicle, and the plastic, sponge and leather of the e-bike contribute a significant heat release rate (about 90%). The results of this study emphasize that e-bike fires are composite fires, and provide an important reference for the timing of extinguishing e-bike fires. Related Articles | Metrics

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Numerical simulation and analysis of electric vehicle fire isolation and mitigation based on FDS Zhu Xianli, Zhang Jiaqing, Rong Fengyi, Li Guohui, Guo Yi 2026, 45 (4):  43-49.  Abstract ( 86 )   This study addresses the prevention and control requirements of electric vehicle fires by using FDS software to construct a numerical model. Three scenarios were established: no suppression with water mist, overhead water mist application, and water mist wall suppression. The study investigates the heat release rate, smoke diffusion, and temperature field changes of fires caused by thermal runaway of lithium-ion batteries under different water mist isolation and suppression measures. Results indicate that without water mist suppression, the maximum temperature can reach 1 138 °C, with a peak heat release rate of 8.4 MW. Water mist fire suppression systems and water mist walls can effectively inhibit lithium battery thermal runaway. After applying water mist, the overall temperature is controlled within 200 °C, effectively preventing the spread of fire and reducing the impact on surrounding vehicles and facilities. This study analyzes the effectiveness of water mist in controlling lithium battery thermal runaway, verifying its role in reducing fire intensity, delaying fire development, and protecting the surrounding environment. The findings provide data support for optimizing the design and application of water mist fire suppression systems in electric vehicle fires. Related Articles | Metrics

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Experimental investigation on thermal runaway characteristics of large-capacity sodium-ion batteries Guo Pengyu, Wu Jingyun, Wang Tinghua, Zhou Xianwei 2026, 45 (4):  50-56.  Abstract ( 21 )   This study investigates a commercial 185 Ah sodium-ion battery using 0.5C rate overcharge to trigger thermal runaway while employing multi-dimensional real-time monitoring of temperature, voltage, and expansion force. The research reveals that the thermal runaway process occurs in three distinct phases: initial response period （0~50 min）, acceleration period （50~90 min）, and complete thermal runaway period （90~110 min）. The thermal runaway evolution sequentially involves sodium-ion concentration saturation and migration at the negative electrode, sodiation reactions at the positive electrode, ultimately leading to cascade reactions of oxide decomposition and electrolyte oxidation. This study employs multi-parameter monitoring methodology, obtaining expansion force evolution data during the thermal runaway of large-capacity sodium-ion batteries, with results showing exponential growth characteristics reaching a peak value of 2 474 kPa. Related Articles | Metrics

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Experimental study on suppression of jet fire formation from high-temperature combustible gas by copper foam Liu Yang, Ji Huaijun, Chen Xinjian, Li Junwei, Zhang Jiahao, Lai Chenglong, Liu Zhihan 2026, 45 (4):  57-61.  Abstract ( 40 )   Different from the conventional ambient-temperature jet fires caused by fuel leakage in previous studies, the high-temperature combustible gas ejected during lithium-ion battery thermal runaway poses a higher fire risk. In this study, copper foam was proposed to reduce the temperature of high-temperature combustible gas and suppress the formation of jet fires, with methane jet fire adopted for experimental verification. The results showed that the 10 ppi copper foam could reduce the temperature of high-temperature combustible gas to 481 ℃, exhibiting excellent suppression and extinction performance on methane jet fires. The 20 ppi and 40 ppi copper foams also effectively reduced the gas flow temperature; however, the relatively high flow resistance induced lateral deflection of the flame, which posed a risk of heating the battery. Regarding the heat absorbed by copper foam from high-temperature combustible gas, the first 35 s were mainly consumed for self-heat storage of the copper foam, and after 35 s, the heat was mainly dissipated into the environment through external radiation. The effective suppression and extinction time of copper foam on methane jet fire exceeded 100 s. Related Articles | Metrics

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Experimental study on flexible phase change materials for battery thermal management Pan Zhiheng, Zhi Maoyong, Su Bingjian, Xu Qinrou 2026, 45 (4):  62-68.  Abstract ( 19 )   In order to control the maximum temperature better and improve temperature uniformity within battery packs, this study developed a hydrated salt-based flexible phase change material (PCM) and applied it to the thermal management of lithium-ion batteries. The results demonstrated that with the addition of 40% silicone rubber, the flexible PCM exhibited a phase change temperature of 45.3 ℃, a phase change enthalpy of 123.2 J/g, and a thermal conductivity of 0.35 W/(m·K), alongside excellent anti-leakage properties, thermal stability, and flexibility. Compared to air cooling, the PCM-based cooling approach reduced the maximum temperature of a single battery under a 2C discharge rate at room temperature (25 ℃) to 58.61 ℃, representing a 7.52 ℃ decrease. For the battery pack, the maximum temperature dropped by 13.48 ℃, and the maximum temperature difference decreased by 7.82 ℃. Furthermore, under high-rate discharge conditions, the PCM-based cooling exhibited superior thermal management performance compared to low-rate discharge scenarios. By using hydrated salt phase change material as a protective layer, the maximum temperature of thermal runaway in the battery adjacent to the heating plate was reduced by 440.8 ℃, effectively blocking the spread of thermal runaway in the battery. The mechanism of phase change materials in battery thermal management and thermal runaway propagation barrier was explored, mainly due to the multiple heat absorption of hydrated salt phase change materials and the formation of porous insulation layers. Related Articles | Metrics

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Study on the development process of bamboo line touch fault and its fault feature extraction in low voltage line Ning Xin, Chen Long, Yu Rui, Zhang Pengfei, Liu Longchen, Zhang Hua, Xiong Jiayu 2026, 45 (4):  69-75.  Abstract ( 28 )   When the bamboo wire touch fault occurs in the low-voltage side of the distribution platform area, it is very easy to produce discharge, and there is a risk of causing hill fire, so fast and accurate identification of bamboo wire touch fault is an important means of preventing hill fire. Based on this, this paper builds a 380 V/220 V low-voltage bare wire-bamboo touch fault simulation experimental platform, establishes the equivalent resistance model of the bamboo touch single-phase conductor faults, through the experiments show that, in the equivalent resistance prediction model range of the bamboo touch single-phase conductor faults with low leakage currents, there is almost no possibility of starting a hill fire. The whole process of line phase-to-phase discharge breakdown and fire caused by a two-phase conductor clamped bamboo fault is reproduced, and a fault signal feature extraction method based on the slope statistic of the high-frequency signal is proposed. The characteristics of the bamboo line touching fault are characterized by the high-frequency discharge energy change, and its effectiveness is verified by experimental data. Related Articles | Metrics

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Time-domain modelling of leakage currents for single-phase touch-tree ignition in 10 kV distribution networks Chen Jinwen, Sun Zhang, Ning Xin, Zhang Hua 2026, 45 (4):  76-82.  Abstract ( 33 )   Tree-contact Single-phase-to-ground Fault (TSF) in distribution lines is prone to cause wildfire, which jeopardizes the safe operation of power systems. Aiming at the problems of insufficient field data of TSF, weak electrical characteristics of leakage current, and less proprietary model research, this paper builds a true-type test platform of TSF in 10 kV distribution network, and explores its ignition mechanism by analyzing the data of TSF phenomenon, vegetation temperature, leakage current and equivalent resistance value. Focusing on the heat accumulation phase before the TSF open fire drifting, a time-domain model of leakage current integrating vegetation size, moisture content and ambient temperature was developed. The correlation coefficient R2 between the simulated and measured RMS leakage current waveforms is verified to be 0.972 6, and the robustness and accuracy of the model is further verified by changing the initial test conditions (vegetation size, water content, and ambient temperature) and comparative analysis of the model. The research results lay a foundation for early failure identification of TSF, which is of great value for improving the prevention and control of wildfire. Related Articles | Metrics

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Research on fault phase selection method considering impedance characteristics of single phase bamboo contact Li Haiyu, Sun Zhang, Song Xiaoxiao, Ning Xin 2026, 45 (4):  83-89.  Abstract ( 20 )   A fault phase selection method considering the impedance characteristics of single-phase contact bamboo is proposed to solve the problem of mountain fire caused by single-phase contact bamboo fault in flexible grounding distribution network. Firstly, a 10 kV single-phase bamboo fault test platform was built, and the ignition characteristics and fault evolution rules of bamboo were systematically analyzed, as well as the correlation between ignition threshold and leakage current, transition resistance and other parameters, revealing the mechanism of mountain fire caused by dead time in the traditional phase selection process; Then, based on the constructed flexible grounding distribution network model, the active phase selection trigger mechanism is introduced to significantly improve the ability of the protection to withstand the transition resistance by continuously injecting the characteristic current and monitoring the characteristic variation; Furthermore, the phase selection process is optimized, the quick response function of trigger phase selection is realized, and the problem of dead time in the phase selection process is solved; Finally, simulation analysis and field tests show that the proposed method effectively reduces the risk of mountain fire caused by single-phase bamboo contact fault. Related Articles | Metrics

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Research on DC arc fault detection algorithm for photovoltaic systems based on ArcNet architecture Wang Yue, Zhang Wang, Cui Hao, Wu Shuhui, Bi Xiaoyang 2026, 45 (4):  90-96.  Abstract ( 29 )   DC arc faults often result in fire accidents, therefore, accurately identifying arc faults is crucial for ensuring the safe operation of photovoltaic systems. Traditional fault detection methods face limitations in handling the variability of arc characteristics, dependence on feature extraction, and real-time processing. To address these issues, this paper proposes an arc fault detection algorithm based on the ArcNet architecture. This method combines multimodal data, including current, voltage, and solar irradiance, to provide efficient and accurate fault identification. Data from a photovoltaic system fault testing platform, including both normal and arc fault data, was collected. The key characteristics of arc faults were identified, and the ArcNet algorithm was designed based on these findings. Experimental results show that the overall accuracy of the ArcNet algorithm on the test set is 98.05%, with a false alarm rate of 1.79% for normal data and an undetected rate of 2.59% for arc fault data. Compared to traditional algorithms, ArcNet shows significant advantages in terms of accuracy, false alarm rate, and undetected rate, which will provide effective technical support for the safe operation of photovoltaic systems. Related Articles | Metrics

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Study on the influence of flexible obstacles on the explosion propagation characteristics of combustible gas in confined space Hu Yang, Lyu Shuo, Song Minhang, Geng Chang, Liu Yijun 2026, 45 (4):  97-103.  Abstract ( 17 )   In order to explore the propagation characteristics of urban gas explosion in the confined space of civil building structures, a circular explosion shock pipe with a length of 12 m and an inner diameter of 90 mm was used to simulate the real explosion scenario, and biaxial stretched polypropylene film (BOPP film) was used as flexible obstacles to simulate destructive building structures such as doors and windows. A methane/air premixed gas explosion experiment with a volume fraction of 9.5% was carried out. The results show that the flexible obstacle film made of polypropylene material has a significant influence on the excitation effect of methane explosion, which can change the evolution process of pressure wave system and accelerate the flame propagation speed. After the film breaking, the pressure wave changes from a continuous weak disturbance wave to a sudden shock wave, and the maximum flame propagation speed increases to 177.30 m/s, which is 3.37 times that of the maximum flame propagation speed under the condition of no film. The gas conditions before and after the film also have a significant influence on the explosion pressure. If the region behind the film is combustible gas, the flame moving at high speed after the film is broken will react with the combustible gas and produce detonation phenomenon, making the maximum pressure as high as 1 634.08 kPa and the maximum flame propagation velocity as high as 671.14 m/s. At the same time, Schlieren technique was used to record the superposition of new shock waves and multi-channel shock waves during the evolution of wave system after film breaking. Related Articles | Metrics

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Construction of a two-phase leakage model based on the properties of LPG components Yu Yilan, Su Longlong, Fu Yufei, Li Longshuo, Ge Weiwei 2026, 45 (4):  104-109.  Abstract ( 29 )   This study uses Aspen Plus software to draw the vapor-liquid equilibrium phase diagram of the propan-butane binary system based on the physicochemical properties of propane and butane. Through analysis, it was found that after LPG leakage, propane in the liquid phase will immediately vaporize, while butane will form a liquid pool and then evaporate and vaporize. Based on these findings, two distinct leakage models for propane and butane were developed respectively. Subsequently, after calculating key parameters such as intermolecular forces, diffusion coefficients, and explosion limits of mixed gases, a two-phase LPG leakage model was established through multi-source gas leakage numerical simulation method. Through the simulation of a LPG tanker leak accident, it was found that propane and butane exhibit completely different gas concentration distributions during the diffusion process, which affects the entire hazardous area. Therefore, the influence of component factors cannot be ignored when simulating LPG leak accidents. Comparative analysis with the Burro 8 experimental dataset demonstrates favorable agreement, validating the model's capability to accurately replicate real-world LPG leakage scenarios. Related Articles | Metrics

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Theoretical analysis and experimental study on the influence of radiant heat transfer on flashover in indoor fires Li Junnan, Fu Yanyun, Zhu Yanbo 2026, 45 (4):  110-115.  Abstract ( 22 )   Thermal radiation is the dominant mode of heat exchange in indoor fires, and it is of great significance for studying the flashover mechanism. By analyzing the radiant heat transfer processes of vertical flames, hot smoke layers and lining materials, a theoretical model of multi-surface radiant heat transfer in indoor fires was established, and the mathematical expression of the radiant heat flux received by combustibles at the floor center was derived. The influence of radiant heat transfer processes in indoor fires on flashover occurrence was explored, and the theoretical model was verified and modified through small-scale experiments. The results show that only 0.2% to 2.0% of the heat radiated by the flame located at the corner reaches the center of the floor, which is less than 0.7% in most cases, indicating that the radiation effect of vertical flames on combustibles horizontally placed on the floor is negligible. The prediction accuracy of the modified theoretical model can reach 80% before flashover occurs. Combined with the radiant heat flux criterion at flashover, the height of the smoke layer interface when flashover occurs can be predicted. Related Articles | Metrics

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Construction of maximum temperature rise model for lateral openings in multi-formation subway carriages in fire Zhou Yun, Zhu Guoqing 2026, 45 (4):  116-123.  Abstract ( 24 )   To explore the temperature characteristics of lateral openings during multi-formation subway train fires, a full-scale FDS numerical model was constructed and verified with scaled-down and previous experimental data. Different train formation numbers and fire source powers were set, considering two typical fire source positions (middle part/end). Results show that when the fire source is at the center of train, the maximum temperature rise at the opening occurs at the top of openings on both sides adjacent to the fire source, and it decreases as the number of formation increases. When the fire source is at the train end, affected by the unbalanced pressure on both sides, the fire source tilts towards the proximal side. At this time, the maximum temperature rise appears at the top of the lateral opening near the fire source end. Based on the M-Q-H model, a prediction model for the maximum temperature rise at the lateral openings of multi-marshaled subway trains was constructed. This model can output quantitative data for fire prevention and offer reference for the subsequent establishment of a two-dimensional temperature field model of the openings. Related Articles | Metrics

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Study on personnel evacuation behavior in high-speed railway station waiting halls considering panic emotion Xia Runming, Chen Honggen, Li Jing, Guo Junpeng 2026, 45 (4):  124-133.  Abstract ( 33 )   Aiming at the problem that panic emotion impairs the efficiency of emergency evacuation of crowds in the waiting hall of high-speed railway stations, this study focuses on constructing a simulation model of personnel evacuation in waiting halls considering panic emotion based on theories and methods such as the SEIRS model and the OCEAN model. Furthermore, a sensitivity analysis of the influencing factors of panic emotion transmission and a simulation study on the optimal design of key influencing factors were carried out. The results of the sensitivity analysis show that equipment guidance has an extremely significant impact on the final panic ratio, while three factors (crowd size, the number of leaders and individual perception range) exert a significant influence on it. The results of the optimal design simulation indicate that under a given specific scenario, the optimal design values of four key factors (equipment guidance, crowd size, the number of leaders and individual perception range) related to evacuation efficiency can be further calculated. This study can provide theoretical and methodological guidance for the optimization of personnel evacuation behavior in the waiting halls of high-speed railway stations. Related Articles | Metrics

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Experimental study on the suppression and extinguishment of UPS control cabinet cable fire by automatic water mist firefighting system Tian Yongjie, Zhang Wei, Wu Qiyong, Li Longgang, Sun Huazhong, Hu Shi, Zhu Xiaolong 2026, 45 (4):  134-139.  Abstract ( 28 )   This study constructed a simulated experimental platform targeting typical cable fire sources to compare the fire suppression performance of single and dual nozzles arrangement on Uninterruptible Power Supply control cabinets fire. Results indicate that the single nozzle, limited by its coverage range, only extinguished localized fires, while the dual-nozzle system achieved full coverage, suppressing unobstructed cable fires within 60 s. Both spray duration and water consumption complied with the GB 50898—2013. The research validates the applicability of dual-nozzle water mist systems in complex obstructed scenarios, providing an optimized solution for UPS control cabinet fire prevention. Related Articles | Metrics

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Design and verification of a crude oil storage tank protection system based on critical-state CO₂ Wang Long, Bai Yunsong, Wang Xiaofeng, Wu Mingjun, Feng Zongrui, Chen Tao 2026, 45 (4):  140-146.  Abstract ( 25 )   Aiming at the structural particularities and safety risk characteristics of crude oil storage tanks, combined with relevant design specifications, an engineering application design of the critical-state carbon dioxide (CO2) protection system for crude oil storage tanks was carried out. According to the engineered pipe network and the structure of primary and secondary sealing rings of the storage tank determined by the application design, a test platform was designed and built to conduct a feasibility test of the protection system. The results show that the peak inlet pressure of the nozzle at the end of the pipe—the most unfavorable point in the designed critical-state CO2 pipeline—reaches 2.481 MPa, and the discharge pressure is maintained above 1.5 MPa for more than 300 seconds. The minimum ambient temperature at the sealing ring can reach -57.7 ℃, and the maximum CO2 volume fraction is 36%. The test verifies the practical feasibility of the critical-state CO2 pipe network for crude oil storage tanks, and demonstrates that critical-state CO2 has excellent cooling and inerting effects on oil tank fires, which provides a strong basis for the application of critical-state CO2 in the field of oil tank fire prevention and control. Related Articles | Metrics

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Research on thermal protective performance of aramid 1414 protective clothing Li Longfei, Li Xiaoying, Zhang Jinzhong, Li Haihang 2026, 45 (4):  147-153.  Abstract ( 23 )   In practical working scenarios with significant thermal risks such as high temperature and strong thermal convection, flame-retardant protective clothing serves as critical equipment for ensuring personnel safety. The thermal shrinkage behavior of clothing during combustion significantly affects the thermal protective performance of flame-retardant protective garments. This study conducted manikin burn tests combined with 3D scanning technology to obtain the burn injury area percentage, burn location distribution, and 3D point cloud data after combustion. Using Geomagic Studio and Qualify software, multiple characteristic parameters reflecting the thermal shrinkage properties of clothing were calculated, including surface area shrinkage rate and volume shrinkage rate. Through principal component analysis, thermal shrinkage parameters that effectively reflect the thermal protective performance of aramid 1414 protective clothing were identified, and principal component scores were calculated for clothing samples tested in manikin burn experiments. The results showed that clothing with a fabric density of 260 g/m² had significantly lower comprehensive scores than protective clothing with 230 g/m² fabric density, demonstrating superior thermal shrinkage resistance. This further confirms the strong correlation between clothing thermal shrinkage and thermal protective performance, and validates that the thermal shrinkage characteristic values determined in this study can effectively reflect the thermal protective performance of aramid 1414 protective clothing. Related Articles | Metrics

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Research on new fire monitoring and early warning technology for unattended substations Gou Lei 2026, 45 (4):  154-161.  Abstract ( 30 )   To address the key problems that the traditional fire-fighting facilities of unattended substations cannot adapt to the scenario requirements of no on-site personnel disposal and long remote response time, and it is difficult to realize ultra-early fire warning and closed-loop management, in this paper, the simultaneous thermal analysis‒Fourier transform infrared spectroscopy (STA-FTIR) technology is used to carry out pyrolysis characteristic experiments on four types of typical cable materials commonly used in substations, including ZR-YJLV cable outer sheath and insulation layer, PVC sheath, and N-BV sheath. The thermogravimetric law of materials in the critical temperature range of 30 ℃ to 350 ℃, as well as the release characteristics of characteristic gases such as H2O, CO2, HCl and pyrolysis particles are clarified, and the ultra-early characteristic correlation basis of "temperature‒gas‒pyrolysis particles" is established. Based on the experimental results, an ultra-early fire detection system with a four-layer architecture of "perception‒transmission‒processing‒application" is designed. The core of the system is a pyrolysis particle detector based on cloud chamber principle and optical analysis techno⁃ logy, which integrates multi-source perception devices such as AI vision camera and thermal imaging camera, and constructs an intelligent decision-making system based on cloud‒edge‒end collaboration. Through the Internet of Things platform, the system realizes cloud storage and intelligent analysis of data, and can realize intelligent linkage with substation access control, video surveillance and fan control system. Verified by long-term operation at 5 unattended 110 kV/220 kV substations in Hebei Province, the false alarm rate of the system is less than 0.5%, and more than 30 overheating hazards of electrical equipment have been successfully warned, which effectively ensures the safe and stable operation of unattended substations. Related Articles | Metrics

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Study on the influence of natural aging in different climatic regions on the fire safety of three types of fire-resistant boards Zhao Xinjie, Jia Pengfei, Shang Ke, Zhang Tianhao, Huang Hao, Wang Bibo, Hu Yuan 2026, 45 (4):  162-168.  Abstract ( 22 )   Based on China's climatic regionalization standards, the study selected Changchun in the temperate zone, Chengdu in the subtropical zone, and Danzhou in the tropical zone to conduct natural aging tests on three types of fire-resistant boards (A, B, and C). The aim was to investigate the effects of different climatic regions on the physicochemical properties, mechanical properties, and fire safety of the fire-resistant boards. The findings revealed that with changing climatic conditions from temperate to tropical zones, the color difference and degree of surface degradation of the boards worsened, density significantly decreased, hygroscopicity increased, and the declines in internal bond strength and modulus of rupture exceeded safety thresholds. Boards aged under tropical climatic conditions exhibited higher peak heat release rates and toxic gas emissions, significantly increasing fire risk. For Type B boards, the peak heat release rate (pHRR) after natural aging was 573.20 kW/m², much higher than the 218.96 kW/m² observed before aging. Compared to temperate and subtropical zones, the combined effects of high temperature, high humidity, heavy rainfall, and high ultraviolet radiation in tropical regions had a more significant deteriorating impact on the performance of fire-resistant boards. Among the three types, Type A boards demonstrated the best flame-retardant performance, outstanding weather resistance, and smoke suppression stability; Type C boards showed moderate flame-retardant performance but were more sensitive to humid and hot environments; Type B boards essentially lost their flame-retardant functionality after aging, ignited rapidly in humid and hot conditions, and exhibited the poorest fire safety. Related Articles | Metrics

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Study on properties of phenolic foam modified by potassium polysilicate based fire-retardant coating Shang Ke, Hou Pengfei, Lin Tao, Wang JunSheng 2026, 45 (4):  169-174.  Abstract ( 20 )   In order to solve the problems of low carbon residue rate, weak carbon layer strength and smoldering of phenolic foam, this article uses silica sol as raw material, glycerin as dispersant, and potassium hydroxide as curing agent to prepare potassium polysilicate based fire-retardant coating, which is used for flame-retardant modification of phenolic foam to improve the flame retardancy, fire safety and thermal insulation performance. Scanning electron microscope, limiting oxygen index, vertical combustion tester, cone calorimeter, butane spray gun and thermal infrared imager were used to study the microstructure, flame retardancy, combustion behavior and thermal insulation performance of phenolic foam before and after the modification of potassium polysilicate based fire-retardant coating. The results show that 50 to 100 μm thick protective layer is formed on the surface of phenolic foam after the modification of potassium polysilicate based fireproof coating, which significantly improves the flame retardancy, fire safety and thermal insulation performance of phenolic foam. After the modification, the limiting oxygen index of phenolic foam is increased to more than 60.0% with a V-0 level in the vertical combustion test. The peak of heatrelease rate and total heat release decreased by 76.2% and 97.3%, respectively, and the residual carbon content increased from 0.3% of almost complete combustion to 75.0%. Moreover, the dense ceramic carbon layer formed by potassium polysilicate based fire-retardant coating can effectively block the spread of flame and heat, thereby reduce the unexposed surface temperature of phenolic foam. Related Articles | Metrics

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Study of the effect of low air pressure on the multi-wavelength optical properties of aerosols Wang Luyao, Bu Zonghao, Liu Quanyi, Wang Haibin 2026, 45 (4):  175-181.  Abstract ( 17 )   Based on a three-wavelength detection platform and a dynamic pressure-variable temperature test chamber, the effects of low-pressure environments on the optical extinction characteristics of smoke were investigated, and the mechanism by which low pressure affects aerosol particle characteristics was revealed by combining experimental and mechanistic analyses. Fire experiments were conducted under low-pressure environments of 50, 70, 90 kPa to obtain the optical power and particle number concentration data. The results show that the optical power of smoldering smoke decreases with decreasing pressure, with the minimum optical power value significantly decreasing, the rates of decay and rebound both accelerating, and the time to reach the minimum value being significantly advanced. While the optical power of open-flame smoke exhibits an increasing trend accompanied by intensified fluctuations. The variation in smoke particle concentration is closely related to the combustion behavior. Related Articles | Metrics

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Study on the effect of water quality in the Western Sichuan Plateau on the properties of aqueous film-forming foam Guo Yi, Zhang Jiaqing, Wang Dongsheng, Kong Depeng, Gao Pengran 2026, 45 (4):  182-188.  Abstract ( 28 )   With the expansion of Ultra-High Voltage (UHV) transmission projects into remote, high-altitude regions such as the Western Sichuan Plateau, Aqueous Film-Forming Foam (AFFF) extinguishing agents used in compressed air foam systems are being increasingly deployed under challenging high-altitude conditions. This study investigates how water quality variations at different altitudes affect the physicochemical performance of AFFF. Firefighting water samples were collected from locations at elevations ranging from 500 m to 4 000 m across the Western Sichuan Plateau and analyzed for water quality parameters. The influence of water quality on key AFFF foam performance characteristics, including drainage, coarsening, and liquid film properties, was systematically evaluated. Results demonstrate that firefighting water at 4 000 m elevation exhibits the lowest conductivity, while water at 2 500 m elevation shows the highest turbidity. Turbidity significantly affects foam stability, with high-turbidity water samples accelerating foam drainage and coarsening processes, disrupting liquid film structure and compromising film stability. Additionally, high-conductivity water samples reduce drainage time. Divalent ions (such as Ca²⁺ and Mg²⁺) present in water samples can shield intermolecular charges, reducing water polarity and potentially hindering gas molecule diffusion, thereby decreasing coarsening rates, as observed in the 4 000 m elevation water sample. These findings provide theoretical support for the efficient utilization of AFFF extinguishing agents in high-altitude applications. Related Articles | Metrics

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Experimental study on the fire resistance of novel multiphase material on pine wood and cypress tree Zhao Lianjie, Zhang Yi, Kang Yu, Zhang Ping 2026, 45 (4):  189-194.  Abstract ( 27 )   Focusing on wildfire suppression, a novel multiphase material was developed to study the fire protection for pine wood and cypress tree. The fire resistant performance of multiphase material on pine wood and cypress tree was studied by carrying out cone calorimeter test, wood-crib fire test, and full-scale cypress fire test. The results show that the multiphase material can prolong the ignition time of pine board and reduce the combustion characteristics parameters such as heat release rate (HRR), total heat release (THR), CO, and CO2 production. The multiphase material forms a dense barrier layer containing metal elements on the surface of the pine board, which plays the role of heat and oxygen insulation. The multiphase material is better than traditional water-based fire extinguishing agent in inhibiting the burning of wood crib, and it has a good fire resistant effect on cypress. Related Articles | Metrics