To investigate the inhibition mechanism of KHCO₃ inhibitor on polypropylene/propylene two-phase explosion, the inhibition mechanism was analyzed from both physical and chemical aspects by examining flame propagation characteristics, pyrolysis characteristics and chemical reaction kinetic mechanism, revealing the interruption of the explosion reaction process. The results show that KHCO₃ exhibits an inhibitory effect on polypropylene/propylene two-phase explosions with different concentration ratios. KHCO₃ decomposes under heating and absorbs a large amount of heat, and the carbonate produced by decomposition adheres to the surface of PP dust, raising the melting point of PP dust from 160 ℃ to 222 ℃. Meanwhile, the maximum consumption rate of ·H by the reaction KOH + H \underset{}{\rightleftharpoons } K + H₂O reaches the highest value of -0.007 45 mol/(cm³·s). The maximum consumption rate of ·OH by the reaction KOH + OH \underset{}{\rightleftharpoons } KO + H₂O reaches the highest value of -0.011 34 mol/(cm³·s). At high temperatures, KHCO₃ generates gaseous K and KOH at the flame front, which continuously scavenge ·H and ·OH through the K \underset{}{\rightleftharpoons } KOH cycle and convert them into H₂O, thereby achieving explosion suppression.

The practice of suspects using gas explosions to conceal tool marks at crime scenes poses challenges for case investigations, yet research on the retention patterns of cutting tool marks in gas explosion environments remains relatively scarce. This study examines gas rubber hoses cut by household scissors. Using an instantaneous high-temperature experimental platform (heating durations of 200, 400, 600, 800, 1 000 ms) and a full-scale gas explosion experimental platform, combined with digital cameras, stereomicroscopes, and energy dispersive spectrometers, we systematically analyzed and compared the morphological and elemental composition changes on the cut surfaces of the rubber hoses. Results indicate that under instantaneous high-temperature conditions with heating durations below 200 ms, shearing tool marks remain identifiable via stereomicroscopy. When heating exceeds 400 ms, marks become unrecognizable due to severe carbonization and ablation. Comparisons between full-scale explosions and 200 ms instantaneous high-temperature conditions revealed that both scenarios yielded identifiable surface shearing tool marks morphologically. Elemental content differences primarily resulted from varying oxidation environments and thermal intensity. This study provides theoretical foundations and technical support for identifying and analyzing shearing tool marks in gas explosion cases.

The determination standards of explosion index at home and abroad are compared and analyzed from the aspects of determination principle, test device, test concentration, result expression and safety requirements. The requirements of test devices in domestic and foreign standards are the key parts of comparative analysis. It is found that there are significant differences in the flexibility, test principle, result expression and safety requirements of test devices between domestic and foreign standards. The domestic standard needs to be improved in terms of the flexibility of the test device, and it is necessary to refer to the relevant research and standards to formulate more strict and clear regulations. The domestic standard should consider turning to absolute pressure to improve the accuracy and reliability of the test.

This study addresses the critical urban safety issue of lithium-ion battery fires in electric bicycles by analyzing the influence of safety vent orientation on fire development through full-scale burning tests. Results show that e-bike fires generally exhibit three distinct stages in both tests: initial combustion, jet fire followed by stable combustion, and decay leading to extinction. The number of jet fire incidents is closely related to the number of battery cells, whereas the scale of jet flames shows no significant correlation with their sequence of occurrence. When the safety vent is oriented vertically (Test A), the flame temperature directly above it is significantly increased, with an average peak temperature of 181.8 ℃， approximately 16% higher than that observed in the horizontal orientation (Test B). Moreover, the entire e-bike in Test A is fully burned in a "rear-first, then front" pattern, where the front section is directly ignited by a jet flame. In contrast, Test B produces a horizontal jet flame with a maximum projection distance of 2.5 m, but the fire remains confined to the rear section. Additionally, the total heat release rate in Test A is about 1.71 times that of Test B. The study confirms that safety vent orientation significantly influences both fire spread behavior and combustion intensity in lithium-ion battery e-bike fires.

This paper explores the damage risk of adjacent cables when arc ignition occurs in the outer sheath of high voltage cables. Firstly, a high-voltage cable arc ignition test platform was built, the 110 kV flame retardant cable was used as the test material. The typical arc fault conditions were selected to carry out the arc ignition test, and the ignition characteristics of the cable outer sheath were analyzed. Then, the equivalent fire source simulation model was established according to the ignition test data, and the temperature rise characteristics of the sheath combustion were verified. Finally, taking a typical cable tunnel as an example, the temperature distribution simulation and the risk assessment of adjacent cable damage were carried out. The results show that the maximum flame temperature under 4~10 A typical arc condition is 310~725 ℃, and the equivalent fire source power is about 128~275 W. When the fault arc current is less than 8 A, there is no risk of damage to the cables in each layer of the tunnel; when the arc current is 8 A and above, the surface temperature of the upper laying cable on the same side of the fault cable exceeds the safety limit 30 s after the arc fault occurs, and there is a risk of damage.

In order to study the smoke control effect of natural smoke exhaust in the large space of railway station buildings, taking the waiting hall of a large TOD railway station building as an example, numerical simulation and hot smoke tests were conducted to analyze the smoke spread law, spatial temperature field, visibility and volume fraction of carbon monoxide in the waiting hall under different fire scales. The results show that the waiting hall has a large space and strong smoke storage capacity. Under the simulated fire sources of 10 MW and 8 MW, the smoke in the waiting hall can be smoothly discharged outdoors through the natural smoke exhaust windows, and the fire smoke mainly accumulates at the top of the waiting hall without significant settlement. The time required for personnel evacuation is 432 s, which is less than the 1 200 s of the fire danger approaching time, and personnel can evacuate safely. Under the test fire source of 1.5 MW, the smoke can smoothly rise to the top of the waiting hall and trigger the opening of all natural smoke exhaust windows. Due to the large space of the waiting hall, the smoke filling time is relatively long, and it takes 14 min for all natural smoke exhaust windows to open in linkage. The temperature rise in the waiting hall space is inversely proportional to the height, and the temperature rise of the smoke at different heights is all above 15 ℃, and no smoke stratification phenomenon occurs. The smoke control system design of this waiting hall is reasonable and effective, and the research results can provide theoretical basis and data support for the smoke exhaust design of similar large space buildings.

In tunnel fires, cross passages may become pathways for smoke spread after the evacuation function is completed, and subsequent longitudinal ventilation can also affect smoke propagation within the tunnel. Based on the Xuefengshan tunnel fire scenario, this study established an FDS numerical model. A combined fire source consisting of a truck (15 MW) and a car (5 MW) was set using time-sequential ignition to simulate the initial fire conditions and ventilation conditions during the fire decay stage. The influence of parameters such as gas velocity, temperature, and visibility on fire rescue operations was analyzed under these two scenarios. The results indicate that the temperature at the eighth vehicle cross passage near the fire source is higher than that at other cross passages, while the seventeenth pedestrian cross passage on the downwind side of the fire source exhibits the lowest visibility, dropping to 5.83 m at 1 926 s. During the fire decay stage, longitudinal ventilation does not cause significant fluctuations in the fire source but does lead to weakened stratification on the downwind side, resulting in rapid mixing of smoke with air. Overall, during the initial fire stage and the subsequent ventilation stage, the non-accident tunnel and the cross passages on the upwind side of the fire source offer a relatively safe environment for fire rescue operations.

High-pressure fine water mist systems are commonly used in underground substations. Compressed Air Foam System (CAFS), as a measure to enhance firefighting capabilities, is gradually being applied in the fire suppression process of substations. To evaluate CAFS performance in underground substations, this study established a full-scale 110 kV underground substation fire suppression test platform. By adjusting parameters such as flow rate, foam type, and combustion area, the extinguishing effectiveness of CAFS was investigated. Results indicate that the CAFS extinguishing process comprises three distinct phases: initiation, sustained suppression, and flame extinction. Increasing the foam mixture supply intensity significantly accelerates flame expansion and shortens extinguishing time. When supply intensity rose from 13.3 L/(min·m²) to 26.7 L/(min·m²), extinguishing time decreased from 22 s to 7 s. Foam liquid type had minimal impact on extinguishing effectiveness, and the presence of spreading fires had little effect on extinguishing duration. Simultaneously, wall surface cooling rates were influenced by flow rate. Higher supply intensities resulted in significantly lower wall temperatures upon successful extinguishment. Oxygen concentration increased after CAFS activation. As supply intensity increased, oxygen concentration at the moment of successful extinguishment first rose then fell, indicating no direct correlation between the extinguishing process and oxygen concentration changes. Comprehensive analysis suggests selecting a CAFS supply intensity between 17.8~22.2 L/(min·m²) with 3% AFFF foam type.

Traditional fire water supply systems in super high-rise buildings face several challenges, including high hydrostatic pressure, poor water supply timeliness, insufficient system reliability, and limited tactical flexibility. The dry fire standpipe system offers advantages such as low risk, high flexibility, and ease of maintenance, serving as an effective and important tactical supplement and redundancy solution. This paper analyzes the working principle and core advantages of the dry fire standpipe system, characterized by "empty pipe in normal times, water supply in disasters", and demonstrates its technical feasibility by combining domestic fire truck water supply capabilities with field test data. The study focuses on the feasibility and technical pathways for converting temporary fire hydrant standpipes or concrete pump pipes from the construction phase into permanent dry fire standpipe facilities, and proposes specific design recommendations for dry fire standpipe systems in super high-rise buildings. The analysis shows that, when combined with the immediate response mechanism of building mini-fire stations and supported by rapid water supply from fire trucks, the system can achieve effective water supply within 5 minutes after fire confirmation, meeting the "golden time requirements for initial fire control" in super high-rise buildings. This study aims to provide new ideas and technical references for improving the efficiency of firefighting in super high-rise buildings.

This study focuses on addressing thermal comfort challenges associated with the hermetic construction of chemical protective clothing. This study employed a thermal manikin experimental platform to investigate the relationship between air gap thickness and manikin surface temperature under multifactorial conditions by systematically measuring temperature variations across different air gap thicknesses, ambient temperatures, and activity intensities, thereby analyzing the impact of air gap thickness on microclimate heat transfer. The results demonstrate that when the air gap thickness reduced from 55 mm to 10 mm, the temperature rise amplitude of the manikin surface increased, indicating that increasing the air gap thickness significantly reduces the manikin's surface temperature. The manikin's surface temperature increased by 0.89 ℃ at 65 W/m² and 1.54 ℃ at 110 W/m² thermal loads, revealing a positive correlation between temperature rise amplitude and activity intensity. The temperature changes of the manikin corresponding to ambient temperatures of 32, 25, 15, 10 ℃ are 1.59, 1.54, 0.42, 0.12 ℃, respectively. The decrease in the thickness of the air layer results in a significant increase in the temperature rise of the manikin as the ambient temperature increases.