The aim of this study was to evaluate the transport phenomena of smoke flow and vertical temperature distribution in a 21-story stairwell with multiple fire locations and openings. A large eddy simulation (LES) method was used to model the smoke flow in a stairwell model with a set of simulation parameters, wherein the fire heat release rate (HRR) and fire location were varied. Based on the results, a wall attachment effect was found in three-dimensional figures. Moreover, with an increase in the fire HRR, the effects were more pronounced. The simulation results verified that the vertical temperature distribution is an index model with a natural logarithm, where the pre-finger factor and attenuation coefficient increase considerably in accordance with an increase in the fire HRR. Moreover, there was a decrease in the maximum temperature (T_m) with an increase in the fire location factor (h*) due to the upward thermal smoke. Moreover, heat mainly accumulates in the area above a fire source. However, h* has a slight influence on the time required to reach T_m within the range of 53–64 s. Furthermore, the direction of the airflow at each side opening in the stairwell varied in accordance with the variation in the fire location changes, and a regular calculation was carried out.

Certain polymers, such as polyvinylidene fluoride (PVDF), polyimide (PI), and poly (phthalazinone ether sulfone ketone) (PPESK), are commonly used separator materials in batteries. However, during the thermal runaway (TR) processing of batteries, significant heat is released by the combustion of the polymer separator. Therefore, analysis of the fire behaviors of polymer separator materials will facilitate a more comprehensive quantitative evaluation of battery thermal risk. This paper investigated the combustion properties of three types of polymers, namely, PVDF, PI, and PPESK, as potential separator materials by cone calorimetry and thermogravimetry (TG). A series of characteristic parameters, including ignition time (TTI), heat release rate (HRR), smoke production rate (SPR), and total heat release (THR), were evaluated for three polymers and blends (PI/PVDF, PPESK/PVDF) under an external heat flux of 45 or 60 kW/m², respectively. The combustion characteristics and fire hazards of the three polymers and corresponding mixtures were analyzed through the comparative analysis of experimental data and phenomena. Under 60 kW/m², the HRR curves of all polymers presented two peaks, while PI/PVDF and PPESK/PVDF mixtures exhibited one obvious peak. Moreover, the peak HRR (pHRR) for the mixed polymers was higher, indicating a relatively higher fire risk. However, in the application scenario, the mixed state represents the main polymer form as the active separator materials in batteries. The results showed that the specific coupling behaviors were related primarily to the component type. This work will help evaluate the fire risk of polymeric separator materials based on the combustion characteristics to predict the safety of mixtures in batteries and develop new methods for fire suppression.

In recent years, the rapid expansion of low-temperature facilities—such as cold storage and indoor ice and snow venues—has underscored their pronounced vulnerability to fire, as evidenced by multiple severe incidents. Due to their distinct environmental conditions, existing theoretical frameworks, technical approaches, and standards exhibit limited applicability. Consequently, the fire risk characteristics of such facilities remain insufficiently defined, and systematic methods for hazard identification and assessment are lacking. This study conducts a detailed analysis of fire incident data from representative low-temperature facilities to identify the fire risk characteristics across all lifecycle stages, including construction, renovation and expansion, operation, maintenance, and demolition. An integrated framework combining the WBS/RBS (Work Breakdown Structure/Risk Breakdown Structure) matrix and complex network (CN) methods is then proposed to establish a structured methodology for full lifecycle fire hazard identification and classification. The results address critical gaps, including the absence of clearly defined lifecycle fire risk profiles and a robust scientific basis for hazard identification, and provide a technical foundation for lifecycle fire risk management in low-temperature facilities.

In recent years, the rapid expansion of low-temperature facilities—such as cold storage and indoor ice and snow venues—has underscored their pronounced vulnerability to fire, as evidenced by multiple severe incidents. Due to their distinct environmental conditions, existing theoretical frameworks, technical approaches, and standards exhibit limited applicability. Consequently, the fire risk characteristics of such facilities remain insufficiently defined, and systematic methods for hazard identification and assessment are lacking. This study conducts a detailed analysis of fire incident data from representative low-temperature facilities to identify the fire risks characteristics across all lifecycle stages, including construction, renovation and expansion, operation, maintenance, and demolition. An integrated framework combining the WBS/RBS matrix and CN methods is then proposed to establish a structured methodology for full lifecycle fire hazard identification and classification. The results address critical gaps, including the absence of clearly defined lifecycle fire risk profiles and a robust scientific basis for hazard identification, and provide a technical foundation for lifecycle fire risk management in low-temperature facilities.