To investigate the correlation between the pyrolysis temperature of cable insulation materials and the insulation failure temperature of cables, the pyrolysis temperature of cable insulation materials and the insulation failure temperature of cables were obtained respectively through thermogravimetric analysis experiments and radiation heating experiments. In the study, Class 1E cables were used, and the influence of thermal aging on the experimental results was considered. The results indicate that the pyrolysis temperature when the first peak of the DTG curve of the cable insulation material appears is essentially the same as the insulation failure temperature obtained by using the criterion of a one order magnitude of decrease in cable insulation resistance as the determination standard for cable failure, with an error of less than 10%; The pyrolysis temperature when the DTG curve starts to deviate from the horizontal curve is essentially the same as the insulation failure temperature obtained by using the criterion of a two order magnitude of decrease in insulation resistance or by drawing a tangent at the maximum slope of resistance decrease and taking the intersection point with the critical value as the determination standard for cable failure after 120 h and 264 h of thermal aging, with an error of less than 20%; While the insulation failure temperatures obtained by using other cable insulation failure determination standards differ significantly from the pyrolysis temperature.

In response to the problem of insulation failure, signal distortion, and even interruption in the control circuit of exposed fire-fighting equipment under the threat of high temperature in fire, this paper selects NH-KVV-3×2.5 cable commonly used in fire-fighting equipment control circuit as the research object. Through cable fire resistance test and ANSYS simulation, the influence of different thicknesses of fireproof coating applied to metal pipes on the temperature field distribution and insulation failure time of internal cables is studied. The experimental results show that different thicknesses of fireproof coatings have a significant protective effect on cables under fire conditions, delaying the rate of cable temperature rise significantly. However, due to the characteristics of the intumescent fireproof coating itself, excessive coating thickness can lead to a decrease in expansion ratio and a reduction in the amplification of cable insulation failure time. The optimal thickness range for fireproof coatings is 1.5~2.0 mm. The insulation failure temperature of the cable is not affected by the thickness of the fireproof coating, and is basically stable at about 148.7 ℃. The ANSYS simulation results show that as the thickness of the fireproof coating increases, the temperature distribution cloud map of the cable shows that the outermost temperature of the fireproof coating remains basically unchanged, and the temperature in the internal area decreases at the same time during the simulation period. The temperature variation law of the insulation layer obtained from the experiment and simulation agrees well, and the maximum relative error between the function of the outer surface temperature-combustion time-fireproof coating thickness of the wire insulation layer constructed based on simulation and the fitting curve of the experimental data remains within 18.1%, proving that the model has high reliability.

Aging and overloading of high-voltage cables increase fire risks and seriously threaten the safety of power systems. During cable fire spread, melt drip burning can ignite underlying cables, accelerating fire propagation. This study used 110 kV flame-retardant cables as test materials to conduct TG-DSC analysis on the cable sheath and carried out melt drip burning experiments under different spacing conditions. Parameters including droplet mass, cable temperature, droplet flame radiation, and dripping frequency were measured and analyzed. Thermogravimetric results indicate that the pyrolysis process of the flame-retardant sheath mainly consists of two mass loss stages. Pyrolysis begins at approximately 400.0 °C, while melting starts near 420.0 °C. During fire spread in high-voltage cables, the molten sheath drips and burns directly below the cables, forming a more intense three-dimensional fire. Due to the large diameter of high-voltage cables, cracking and detachment of the char layer formed by the flame-retardant material exacerbate dripping combustion. The mass of melt drip residues accounts for about 17%~30% of the total cable mass loss. The distribution of melt drips from high-voltage cables is scattered and highly random. Dripping behavior can be divided into two zones: frequent dripping zone (f ≥ 1) and infrequent dripping zone (0< f <1).

The frequent occurrence of electrical fires is closely associated with AC line faults. Among them, hidden or sudden faults such as ground faults, overload operation, and short circuits pose significant challenges in fire prevention and control, due to limitations of traditional monitoring methods including delayed response and insufficient risk identification accuracy. To address this, this study develops an AC line fault simulation system for electrical fire prevention, which integrates three typical fault modules, including short circuit, overload, and ground fault, and establishes a synchronous multi-source signal acquisition and analysis platform. Experimental results demonstrate that the energy release of short-circuit faults exhibits significant phase dependence. The energy released during a short circuit at the voltage rising edge reaches 158.8 J, an increase of 249.8% compared to the condition at the voltage falling edge. A ground fault without leakage protection causes rapid local temperature rise under a continuous current of 3 A, indicating a fire risk. Overload experiments reveal a nonlinear coupling relationship among wire diameter, current intensity, and temperature rise rate. A 1.5 mm² wire under 56 A overload exhibits a temperature rise rate of 3.32 °C/s, far exceeding that of a 2.5 mm² wire under the same operating conditions. Based on experimental data and distinguishing protection states, a fire risk classification system is established: under unprotected conditions, the risk of a ground fault without leakage protection is higher than that of overload operation; under protected conditions, short-circuit faults become the primary fire hazard due to instantaneous high-energy release accompanied by arcing, while ground faults can be effectively and promptly interrupted by leakage protection. The research outcomes provide data support for setting fire warning thresholds, fault backtracking analysis, and fire evidence identification, contributing practical value to enhancing the active fire prevention capabilities of electrical systems.

The technical value of smart electricity meters data in tracing the causes of electrical fires has become increasingly prominent, yet the data characteristics and their linkage mechanisms with electrical fires still require further exploration. This study systematically analyzes the correlation between electrical characteristics and fire risks under scenarios such as load type identification, single-phase voltage fluctuations, and current anomalies through the construction of a multi-scenario fault simulation experimental platform. The platform integrates smart meter dynamic data monitoring, oscilloscope waveform capture, and infrared thermal imaging technology. Experimental results reveal substantial discrepancies in power factor and reactive power across load types, offering critical evidence for fire site load classification. In the condition of voltage deviations, overvol⁃tage elevates resistive load currents, while undervoltage triggers compensatory current surges in constant-power loads, intensifying conductor overheating. The instantaneous peak current of zero fire short circuit can reach 260 A, releasing more than 100 J of energy. The leakage point temperature of the live wire (65 mA) exceeds 300 ℃ within 1 min, and the temperature rise of the overloaded (1.5 times) wire reaches 104 ℃. The temperature of the inferior wire (0.5 mm2) after normal current flow reaches 173.6 ℃, all of which pose a direct risk of igniting combustibles. The research has verified the technical effectiveness of smart meter data in tracing the causes of fires, and proposed active prevention and control strategies such as mandatory installation of circuit breakers and standardized wire selection standards, providing theoretical support and practical reference for precise prevention, cause tracing, and safety management of electrical fires.

In order to improve the fire protection capacity of the main transformer of 330 kV substation and ensure the safety of the power grid, the paper analyzes the current situation and shortcomings of the fire protection facilities configuration of the main transformer of 330 kV substation, compares the advantages and disadvantages of four main transformer fire protection capacity improvement schemes, namely, fixed foam spray fire extinguishing system, compressed air foam fire extinguishing system, foam water mist vortex fan fire extinguishing system, and robot fire extinguishing system, determines that the robot fire extinguishing system is more suitable for the fire protection capacity improvement of the main transformer of 330 kV substation, and proposes an intelligent foam spray vortex fan robot fire extinguishing system. The test shows that the intelligent foam spray turbofan monitor robot extinguishing system puts out the oil pool fire in 6 minutes, the transformer and radiator top surface fire in 6.7 minutes, the casing spray fire in 7.2 minutes, successfully controls the fire, and extinguishes all open fires in 9.5 minutes without reburning. A typical fire extinguishing system scheme for the main transformer of a 330 kV substation has been designed, providing reference for the subsequent improvement and renovation projects of the fire protection capabilities of the main transformers in 330 kV and 500 kV substations, as well as the design of the fire extinguishing system for new substations.

Against high-voltage transmission tree-line failure, there is relatively little research on residual traces analysis technology. This article built a 10 kV distribution network platform and conducted tree-line fault simulation experiments in combination with outdoor soil environment, obtaining experimental samples of transmi- ssion line and conducting research on forest electrical typical traces analysis technology based on macroscopic/microscopic morphology, Micro CT, and metallographic. The research has shown that tree-line failure in 10 kV transmission lines occur under high voltage and low current conditions, with characteristics such as small melting range, difficult observation of melting transition zone, and susceptibility of conductor surfaces to inorganic burning and invasion from trees. The residual trace morphology of transmission lines at the fault contact points of trees at different positions is closely related to the leakage current during the fault process. As the severity of the fault changes, the microscopic morphology trace characteristics transform from fence like and fish scale like to honeycomb like. Different analysis methods can provide theoretical and experimental basis for the identification and analysis of forest electrical fires caused by tree-line failures from different perspectives.

In order to clarify the reliability of the extra-high voltage transformer station lifting fire robot to transport a variety of fire-fighting agents, Fluent was used for water, foam and compressed air foam in the pipeline with long-distance transport, height changes in the pressure drop numerical simulation study. The results of the study show that: in the range of supply flow 2 000~4 000 L/min, the pressure drop of the three extinguishing agents fluids in the hard pipe increases with the increase of flow rate, and the supply flow 4 000 L/min of each extinguishing agents pressure drop can be up to 3.4 times that of 2 000 L/min. At the same flow rate, the difference in pressure drop between foam and water is small, while the pressure drop of compressed air foam is much greater than that of water and foam. Affected by frictional resistance and local resistance, there is a large pressure drop at the hard hose connection port; changes in the height of the pipe nozzle have a significant effect on the rising section, the higher the height, the faster the pressure drop, the pressure drop coefficient of the pipe at a height of 15 m can reach 1.9 times that of the 6 m pipe.

Fires of oil immersed transformers may cause serious consequences. A dynamic fire risk assessment method was suggested to provide guidance for the prevention and risk management of transformer fires. In this paper, the causes of oil immersed transformer fire are analyzed based on accident cases and industry statistical data. A transformer fire risk index system covering six dimensions including the inherent risks of transformer components, dynamic operation risks, failure risks of ancillary facilities, external environmental factors, reliability of firefighting equipment, and fire safety management level has constructed. A single index classification evaluation method covering four severity levels has proposed. The chain evolution model of transformers fire has developed using complex network method, the index weights are calculated based on the measurement method of node importance. A calculation method for the overall fire risk value and extremely fire risk value of transformers is proposed based on the TOPSIS method, and the application process of the evaluation model is demonstrated through practical examples. The results show that oil temperature rise, short circuit and arc discharge are the most important fire risk points of transformers. The proposed transformer fire risk assessment method can further refine and present the risk conditions of each dimension on the basis of providing the overall risk level. The research results can provide guidance for the dynamic monitoring of transformer fire risks and the implementation decision-making of risk reduction measures.

Lithium-ion battery energy storage, as the core technology of new energy storage, holds strategic significance in promoting energy transition and achieving the "dual carbon" goals. However, with the rapid growth of installed capacity, fire safety issues of energy storage systems have become increasingly prominent, seriously restricting the safety development of this industry. This paper systematically analyzes typical global energy sto- rage system fire cases, summarizes accident characteristics and disaster-causing mechanisms; and comprehensively reviews the research status and development trends of energy storage safety technologies from four dimensions: intrinsic safety, thermal runaway mechanism, monitoring and early warning, and fire suppression and explosion prevention. In terms of intrinsic safety, research on solid-state battery technology and modification of material systems continues to advance; research on thermal runaway mechanisms has evolved from single-characteristic analysis to multi-physics field coupling and cross-scale prediction studies; monitoring and early alarm technologies are moving towards multi-parameter fusion and intelligent diagnosis; fire extinguishing technologies are shifting from comparison of using single fire extinguishing agents to multi-agent application and precise suppression and control. The research indicates that future energy storage fire technologies will develop in a coordinated manner towards the directions of intrinsic safety foundation, systematic mechanism research, intelligent early alarm and diagnosis, and precise fire extinguishing, providing technical support for building high-level safety energy storage systems.

This paper uses a self-built fire extinguishing experimental platform to select expandable vermiculite powder and vermiculite powder modified with MgCl2 and NaHCO3 for lithium-ion battery fire extinguishing experiments. And compared with ABC dry powder under the same working conditions, the fire extinguishing time, temperature rise suppression efficiency, reignition situation, and toxicity suppression of different fire extinguishing agents were analyzed. Fire extinguishing tests have shown that compared with ABC dry powder fire extinguishing agent, vermiculite powder can quickly reduce the surface temperature of the battery and effectively extinguish open flames, providing more uniform coverage and cooling effect. It has been confirmed that vermiculite powder can be used as a new type of fire extinguishing medium in lithium-ion battery fires, but the effectiveness of vermiculite powder is limited as it can reignite after extinguishing open flames. Compared with vermiculite powder, further modification treatment enhances the thermal stability and flame retardancy of modified vermiculite powder, reducing the possibility of reignition significantly. Especially, the MgCl2 vermiculite powder extinguishes the open flames and prevents reignition, which has a good fire extinguishing effect on ternary lithium-ion batteries.

To explore whether the application of liquid water-based medium in battery thermal runaway suppression through immersion would cause secondary disasters and its actual effect on lithium battery thermal runaway suppression, this paper designed a long-term immersion test of a fully charged 1P9S-280 Ah series battery module in liquid water-based medium, as well as the suppression of thermal runaway propagation using liquid water-based medium. The results showed that an 840~8 370 kΩ resistance was formed between the positive and negative terminals of the battery after immersion in liquid water-based medium, indicating weak discharge of the battery in this medium and no risk of secondary disasters. Following the application of liquid water-based medium, the maximum temperature during the battery thermal runaway of the 1P9S-280 Ah battery series module was 398.1 ℃, and the maximum temperature of adjacent batteries was 125.6 ℃, demonstrating the significant suppression effect of liquid water-based medium on battery thermal runaway intensity and propagation.

Against the safety management and risk control problems of hydrogen refueling stations, using simulation and mathematical analysis, explore the dynamics of small leakage and diffusion of liquid hydrogen while assessing the interactive effects of temperature and wind speed. The results indicate that a small leakage of liquid hydrogen results in the rapid formation of a hydrogen cloud, with its diffusion distance markedly increasing as wind speed escalates. In the absence of wind, the hydrogen cloud spreads to a distance of 12 m from the leakage port within 30 s. When the wind speed reaches 3.06 m/s, the cloud extends to 24 m, and at 5.59 m/s, it expands to 28 m. However, higher wind speeds can lead to hydrogen accumulation in lower altitudes, necessitating adjustments to wall height. Additionally, a rise in wind speed facilitates the dilution of the hydrogen cloud. At normal temperatures, the hydrogen mole fraction drops by approximately 7.53% compared to low wind speeds, and by roughly 5.98% at lower temperatures. Conversely, at higher temperatures, the evaporation of liquid hydrogen accelerates, augmenting both the initial concentration and diffusion range of the hydrogen cloud. Both temperature and wind speed have a combined influence on the initial concentration, diffusion range, and final stable concentration of the hydrogen cloud. When devising safety measures, factors such as wind speed, temperature, and potential fire sources must be thoroughly considered. Particularly under conditions of high temperature and high wind speed, it is imperative to enhance real-time monitoring and emergency preparedness.

A study on the fire suppression characteristics of lithium iron phosphate energy storage battery modules during the early stage of thermal runaway was conducted based on a micro fire suppression module. The module was filled with a ternary mixed fire extinguishing agent developed in earlier research by the project team. The experiment used overheating as the trigger condition and obtained key parameters such as temperature rise during battery venting and thermal runaway, critical temperatures, and fire suppression behavior characteristics, which can provide guidance for fire prevention in energy storage battery packs. The micro temperature-sensitive automatic fire suppression module can extinguish the initial fire of a lithium iron phosphate energy storage battery module during thermal runaway within 3 seconds. If no ignition sources such as open flames or electric sparks are present, the battery fire does not reignite. By pre-installing micro fire suppression modules in energy storage battery packs, fire protection can be provided during transportation, installation, and other scenarios where effective safety measures are unavailable.

Based on fire dynamics principles, we investigate the combustion characteristics of fuels and the heat radiation transmission mechanisms of smoke in forest fire. Key combustion parameters for three common tree species in North China（Pinus tabuliformis,Sophora japonica,Populus davidiana）were measured using a cone calorimeter. A three-dimensional combustion numerical model was constructed with PyroSim software to analyze the effects of wind speed, ambient relative humidity and canopy structure on smoke heat radiation transmi- ssion. The results indicate that when wind speed is below 6 m/s, thermal radiation intensity increases with wind speed; however, when wind speed exceeds 6 m/s, enhanced turbulence restricts smoke plume diffusion, reducing thermal radiation intensity by 12%~16%. For every 15% increase in ambient relative humidity, thermal radiation intensity increases by 0.5%~1.6%, though this enhancing effect exhibits significant spatial heterogeneity. Canopy structure alters local turbulence intensity near the trees, leading to notable differences in thermal radiation intensity distribution. The findings provide theoretical support for understanding heat transmission mechanisms in forest fires and offer scientific references for optimizing firefighting tactics.

In order to study the fire extinguishing technology and measures for rubber tire fires, and further improve the ability to deal with such fires, this article investigates the material characteristics of rubber tires by referring to relevant domestic and foreign literatures, analyzes the combustion principle and fire spread and expansion process of rubber tires, and compares the key technical indicators of rubber tire fire extinguishing agents by setting up test equipment to test the fire extinguishing efficiency of fire extinguishing agents; And through experiments and relevant cases and literatures at home and abroad, summarize and generalize the characteristics and disposal difficulties of rubber tire fires. Based on fire cases and experimental conclusions, further develop rubber tire fire extinguishing actions, fire extinguishing and disposal procedures, and fire extinguishing technology applications.

Under fire exposure, the mechanical properties of steel structure materials deteriorate, which is prone to causing fire-induced failure of steel members. Monitoring the temperature of structural members and establishing early warning and prediction methods for their fire-induced failure have long been the focus of fire fighting and rescue personnel. This paper studies the early warning and prediction technology for fire-induced failure of steel structure columns and its application method in actual building fires. An early warning system for fire-induced failure of steel structure columns based on temperature monitoring is developed and verified through fire tests on H-shaped steel short columns. The results show that the developed early warning system can realize over-heating warning inside the building, over-heating warning at the external rescue command center, and real-time monitoring of ambient temperature, and can provide early warning and prediction for fire-induced failure of steel structure columns in building fires.

Compared with other fibers, ceramic fiber is characterized by high temperature resistance and exce- llent impact resistance. In order to promote the application of ceramic fiber in the field of concrete materials, the impact resistance of ceramic fiber modified concrete (CRFMC) with different fiber volume content (0.1%, 0.2%, 0.3%) after different high temperatures (200, 400, 600, 800 ℃) is studied with high temperature test and separated Hopkinson pressure bar test. The modification mechanism of ceramic fiber is analyzed by observing the micromorphology of CRFMC after different high temperature test. The results show that ceramic fiber can improve the impact resistance of concrete after high temperature test, and the optimal content of ceramic fiber is 0.2%. With this fiber content, the damage degree of CRFMC is the lightest, and the dynamic compressive strength, dynamic peak strain and impact dissipation energy are the maximum. With the rise of temperature, the damage severity degree, dynamic compressive strength and impact dissipation energy of CRFMC first decrease and then increase, and the dynamic peak strain increases. The dynamic peak strain of CRFMC shows a thermoplastic effect. Ceramic fiber still maintains good shape after high temperature test, and is not decomposed or fused. The improvement effect of ceramic fiber on dynamic compressive strength and impact dissipative energy of concrete at high temperature (400~800 ℃) is better than that at 20 ℃.

As the power center of a ship, the engine-room contains a wide variety of equipment with complex structures, numerous hazard sources, and high risk levels, making it prone to fires. Therefore, engine-room fires have always been a critical issue in ship fire safety. Based on a summary of the hazard sources and characteristics of engine-room fires, this paper elaborates on typical fire parameters and establishes three hazard criteria based on their impact on personnel: flue-gas temperature, oxygen volume fraction, and visibility. Common types of engine-room fires include oil pool fires, jet fires, electrical cabinet fires, and cable fires. Focusing on the most common oil pool fire, this study constructs experimental scenarios in a closed test cabin. For five different oil pool areas (0.25, 0.50, 1.00, 2.00, 4.00 m²), the fire evolution patterns are investigated and summarized in terms of heat release rate, flue-gas temperature, visibility, oxygen volume fraction, and other parameters.

An interpenetrating network hydrogel fireproof glass was developed to address the shortcomings of insufficient thermal insulation and weather resistance of polyacrylamide hydrogel fireproof glass. The interpe-netrating network hydrogel fireproof glass was prepared with polyacrylamide (PAM) as the first network and polyethylene glycol 2000(PEG2000) as the second network. The effects of PAM/PEG interpenetrating network structure on the light transmittance, thermal insulation and weather resistance of fireproof glass were studied by light transmittance tester, simultaneous thermal analysis-fourier transform infrared spectroscopy tester and cone heater. The results show that the construction of PAM/PEG interpenetrating network effectively improves the thermal insulation performance of fireproof glass while slightly maintaining a high degree of transparency affecting the light transmittance. Increasing the content of PEG2000 in PAM/PEG fireproof hydrogel can greatly promote the enhancement of interpenetrating network structure and endow fireproof glass with more excellent weather resistance. When the addition amount of PEG2000 is 4%, the fireproof glass shows excellent comprehensive performance. The backside equilibrium temperature at 3 600 s after 168 h artificial accelerated aging decreases by 46.0% compared to that of the fireproof glass without PEG2000.

Early fire detection in high-rack storages is challenging due to dense cargo storage, complex structural configurations, and lighting interference. To address this issue, a lightweight deep learning algorithm that fuses visible and infrared images is proposed. The method employs a dual-stream feature extraction network and incorporates a cross-modal feature complementation mechanism to effectively enhance the recognition capabi-lity for smoke and flame characteristics. Additionally, a DFASC-IPV auxiliary module based on video grayscale variation analysis is designed to effectively suppress light source interference and enhance responsiveness to thin smoke. Experimental results demonstrate that compared with single-modal methods, the proposed approach achieves an accuracy improvement of 11.46% and a recall improvement of 13.14% in complex storage scenarios, exhibiting excellent robustness and practicality. This research provides a reliable technical solution for early fire detection in high-rack storages.

In order to improve the flame retardant performance of silicone rubber foam (SiFs), manganese phytate (PA-Mn) was prepared by direct precipitation method, and Fourier transform infrared spectroscopy, X-ray optoelectronic spectrum and scanning electron microscope.PA-Mn with the mass fraction of 1%, 3%, 5%, 7% and 9% was added to SiFs, and the performance of ultimate oxygen index (LOI) tester, vertical combustion tester (UL-94) and cone thermometer were analyzed. The results show that the PA-Mn prepared by direct precipitation method has high purity. PA-Mn can significantly improve the flame retardant and smoke suppression properties of SiFs. When the addition amount is 3%, the flame retardant and smoke suppression properties of SiFs are the best. The LOI is 28.2%, reaching UL-94 V-0 grade. The peak heat release rate, total heat release and fire growth index are 27.4%, 16.1 % and 36.4% lower than those of pure SiFs, respectively. The fire performance index is 22.2% higher than that of pure SiFs, and the smoke density grade, maximum smoke density and total smoke production are 5.5%, 19.8% and 16.6% lower than those of pure SiFs, respectively.

Continuous and efficient anti-reignition and explosion suppression is the key to combat the thermal runaway fire of large-capacity lithium-ion battery. A new type of fire extinguishing and explosion suppression device using carbon dioxide-perfluorohexanone compound is proposed. The mixed compatibility test of liquid CO2 and perfluorhexanone was carried out, and the cold spray test, energy consumption analysis and simulated fire extinguishing test of large-capacity battery module were carried out. The results show that the low temperature and low pressure liquid CO2 stored at -20 ℃ can be completely miscible with perfluorohexanone in the range of 0~1.7 mass ratio to form a composite fire extinguishing medium. The composite fire extinguishing agent system can realize one-time injection and intermittent injection. The annual power consumption of fire extinguishing and explosion suppression system is only 10.48 kWh, with low power consumption and favorable economic performance. In the fire extinguishing test of 314 Ah lithium iron phosphate battery module, the open flame of the battery was extinguished within 1 s, no reignition and thermal runaway spread occurred, the single point temperature was as low as -72 ℃, and the cooling and anti-reignition and explosion suppression performance was excellent. Research results can provide a new efficient and economical solution for fire extinguishing and explosion protection of lithium batteries.

Hydrogel fire extinguishing agents can remarkably increase the utilization rate of water and improve fire extinguishing performance in forest fire fighting. At present, there is little research on solid-liquid mixing devices based on hydrogel fire extinguishing agents, and there is a lack of accurate and reliable prediction models. In this study, experiments have been conducted to evaluate the effects of inlet operating conditions and geometric structure on the ejection characteristics of Venturi-type solid-liquid mixer for hydrogel fire extinguishing agents. The results show that the ejection coefficient of the solid-liquid mixer is positively correlated with the inlet velocity of the working fluid. The mixing efficiency of the mixer increases with the increase of the nozzle outlet diameter or the inlet diameter of solid particles. Additionally, the mixing efficiency shows a trend of first increasing and then decreasing with the increase of the working fluid inlet velocity. Based on the experimental results and Buckingham's Π theorem, a prediction model for the ejection characteristics of the solid-liquid mixer for hydrogel fire extinguishing agents is established to provide a theoretical basis for the design of solid-liquid mixing devices based on hydrogel fire extinguishing agents.

Foam extinguishing agents are one of the effective methods for combating oil fires; however, there are numerous types with significant variations in their compositions, and the compatibility issues among different types of foam extinguishing agents need to be explored. This study selected three typical low-expansion foam extinguishing agents: aqueous film-forming foam (AFFF), fluoroprotein foam (FP), and synthetic foam (S). These were mixed in five different ratios in pairs, and physical-chemical and extinguishing experiments were conducted to systematically analyze the effects of the mixing types and ratios on drainage time, coarsening rate, spreading process, and extinguishing time. The results indicate that adding a small amount of FP to AFFF can enhance its foam stability to some extent, as evidenced by slower drainage and coarsening rates, while AFFF/S and FP/S mixed foams showed poorer stability. Furthermore, due to the enhanced stability, the AFFF/FP mixed foam exhibited better extinguishing performance at a mixing ratio of 3：1. The FP/S mixed foam, due to its lower stability, required the longest time for extinguishing, indicating poorer performance. Therefore, AFFF and FP demonstrate a certain degree of compatibility and can be mixed in specific ratios under certain conditions.

In order to improve the flame retardancy and anti-aging properties of rigid polyurethane foam (RPUF), a composite RPUF was prepared by using dimethyl methylphosphonate (DMMP), chitosan containing 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) (CS-L) and KH-550 modified molybdenum tailings (MT) as a flame retardant system. Infrared spectroscopy (FT-IR), color difference, water contact angle (WCA), compressive strength, thermal conductivity, limiting oxygen index (LOI), vertical flame test (UL-94), cone calorimeter (CC) and thermogravimetric analysis (TG) were used to study the performance changes of composite foams containing different flame retardant components before and after aging. The fire performance index (FPI) and fire growth index (FGI) of the foam before and after aging were calculated to evaluate the fire risk change of the material after aging. The results show that the DMMP/CS-L/MT composite RPUF has better flame retardancy and aging resistance. The composite foam shows reduced photodegradation and hydrolytic degradation, smaller color differences, increased hydrophobicity, improved compressive strength, and lower loss in flame retardancy.

In the traditional intumescent flame retardant system, the poor interfacial compatibility between ammonium polyphosphate (APP), as the acid source, and epoxy resin (EP) is a common problem, resulting in the need for a higher additive amount to achieve a good flame retardant effect. In order to solve this kind of problem, this paper synthesized a core-shell structural material APP@CS with APP as the core and chitosan (CS) as the shell to improve its compatibility with EP, and at the same time synthesized an aminophenol-formaldehyde resin (APS), which has better compatibility with EP matrix, as the carbon source of intumescent flame-retardant system. Thermal analysis results show that EP/8%APP@CS/APS has a significant increase in residual carbon of about 173% compared to EP. In terms of flame retardancy, EP/8%APP@CS/APS passed UL 94 V-1 rating with an ultimate oxygen index of 31.6%. The peak heat release rate, total heat release rate, total smoke emission, and smoke release rate of the EP/8% APP@CS/APS composite were reduced by 78.0%, 55.1%, 54.5%, and 58.3%, respectively, compared to pure EP. The above results show that APP@CS and APS have synergistic effects in improving the thermal and flame retardant properties of EP.

To alleviate occupational burnout among firefighters, scales measuring exercise self-efficacy, occupational burnout, physical activity, and perceived social support were used to assess the mental health status of 408 front-line firefighters. The study explored the relationship between exercise self-efficacy and occupational burnout among firefighters, examined the mediating role of physical activity and the moderating effect of perceived social support, and proposed corresponding optimization strategies. Results indicate that exercise self-efficacy can directly predict burnout levels and indirectly influences burnout through physical activity. Perceived social support moderates the effect of physical activity on occupational burnout, with the mediating effect being more significant in groups with moderate to high levels. Based on these findings, multidimensional coping strategies are proposed: improving sports facilities and developing personalized training programs; introducing novel sports activities and establishing a scientific incentive system; strengthening social support networks and implementing routine mental health monitoring.

With the expansion of the "all disaster and major emergency" work functions of China's fire brigade, the demand for firefighting protective clothing is gradually increasing. Developers need to iterate and optimize the firefighting protective clothing by comparing advanced products at home and abroad. Based on the existing work foundation and market research, this article summarizes, compares, and analyzes the current status of firefighting protective clothing used by firefighters at home and abroad in recent years, providing reference for product development. At the same time, according to the analysis results, it was found that there are still many problems with the firefighting protective clothing that need to be solved urgently, and the development trend of the firefighting protective clothing in terms of domestication, comfort, lightweight, and intelligentization in the future are explored.