Fire Technology最新文献

The use of external fire suppression systems can reduce the risk of fire spreading between buildings. This study investigated the effectiveness and efficiency of different externally placed water-based fire suppression systems on façade fire safety. A series of large-scale experiments comprising an SP Fire 105 setup equipped with sprinklers and high-pressure water mist nozzles have been performed. A combustible façade, consisting of 2.5 cm thick oriented strand board (OSB) plates, was installed to provide challenging conditions and allow a visual assessment of the post-fire damage. The temperature profile on the façade surface was measured with 34 thermocouples, while five heat flux gauges and two fast-response plate thermocouples were used to measure the heat flux on the façade surface and emitted to the ambient. The sprinklers and the high-pressure water mist system effectively suppressed the upwards flame migration and reduced the heat flux toward adjacent buildings. It was observed that the sprinklers acted as a water curtain and kept the façade wet during the fire, promoting minor damage (the burnt area is less than 1% of the total area). The temperature and heat flux measurements demonstrated that the sprinkler system was the most effective suppression system. However, the high-pressure water mist systems achieved similar effectiveness but a much higher efficiency concerning water consumption. The sprinkler nozzles used four times as much water as the high-pressure water mist nozzles.

This study employs a combination of theoretical analysis, Similarity simulation, and computational fluid dynamics (CFD) to examine the airflow caused by the stack effect under different leakage conditions in high-rise buildings and the transport of fire smoke. Building on previous research, we quantify the leakage area using a formula and classify it into two categories, "tight" and "leaky." Based on the analysis results, we conduct a similarity simulation experiment in a small-scale high-rise building experimental platform with a height of 5.2 m to create a certain size of leakage area at the bottom and record carbon monoxide concentration at different locations and times. The obtained result is then compared with the numerical simulation result, and the similarity simulation results match well with the numerical simulation results. The findings demonstrate that increasing the leakage area accelerates the transport of smoke due to the stack effect, particularly at higher floors. This paper also discusses strategies to impede smoke diffusion, providing valuable references for the safety design of high-rise buildings.

Accurate fire ignition spatial location methods can serve the automatic fire suppression based on video. Although current fire detection systems based on monocular surveillance videos can quickly detect fires, it is impossible to obtain the 3D position due to the polysemy of 2D images. To further promote the universal application of automatic fire suppression, we propose a 3D indoor fire ignition location method based on monocular vision. This is the first study on spatial orientation of fire based on monocular vision. First, the indoor scene is quickly reconstructed as the basis of the scene. Second, based on our previous research on fire detection, the refined position of the fire in 2D images and its topological relationship with the space object are analyzed. The hierarchical constraints from 2 to 3D are established for the spatial orientation of the indoor fire ignition point. The experimental results show that the average absolute error is only 4.82 cm and that the average relative error is 1.71%. In addition, our method can be embedded into the existing fire prevention and control system at a low cost, further promoting the development of intelligent fire prevention and control.

Nano SiO₂ particles (NPs) combined with organosilane surfactants present a promising avenue for the development of stable fluorine-free firefighting foams. In this study, hydrophilic nano SiO₂ particles, non-ionic organosilane surfactant (SiCare2238), and amphoteric hydrocarbon surfactant (LAMC) were prepared as a mixed dispersion to investigate the interactions between nano particles and surfactants, foaming ability, and foam stability of the mixed dispersion. Results indicated that the surface activity, electrical conductivity, and foaming ability of the mixed dispersion decreased with increasing NPs concentration. The impact of NPs on foam stability depended on the filling and blocking mechanisms within the platform boundary of the formed liquid film. At NPs concentrations below 1.5%, strong electrostatic interactions among surfactant molecules resulted in the adsorption of surfactant molecules on the nano particle surface, preventing the formation of a network structure at the platform boundary, thereby reducing foam stability. At NPs concentrations above 1.5%, a significant number of NPs formed a network structure, filling and blocking the platform boundary, leading to delayed foam drainage, coarsening, and enhanced foam stability. This study provides theoretical guidance for the application of nano particles in fluorine-free.

The study aims to analyze risk perception, through the psychometric paradigm, and to identify the influencing sociodemographic factors, in a sample of Portuguese firefighters. This is an exploratory, cross-sectional study, involving an online questionnaire, in a convenience sample of (n = 59) firefighters from corporations in two Portuguese cities. The firefighters’ risk perception in the sample is high (mean 8.61). Considering the psychometric paradigm dimensions, fear of suffering damage, personal vulnerability, severity of injury or disease, catastrophic potential and long-term consequences are those that influence risk perception in the sample. Firefighters consider to be exposed to a high level, to ergonomic risks, night shifts, chemical agents, thermal stress, stress, biological risks, risk of burn and explosion. Firefighters with < 5 years in service presented the lowest mean of risk perception (p-value = 0.022), but the sociodemographic variables, type of professional bond or the number of accidents suffered presented no significant difference (p-value > 0.05). To evaluate the self-reported adoption of safety behavior, the respondents classified their agreement with statements related to: the compliance with safety rules and procedures, the use of PPE, the attitude towards safety training and work pressure. It was concluded that the respondents who have a higher risk perception tend to adopt safety behaviors, thus confirming the importance of risk perception to implement targeted and effective strategies in safety training. Firefighters in the sample with fewer years of service have a lower risk perception, so they should be considered as a priority segment for safety training.

The structural system of eccentrically braced frames (EBFs) is one of the most common structural systems with a excellent seismic performance in highly seismic areas. This study investigates the performance of this structural system in low-rise buildings. For this purpose, a three-story structure with this structural system is designed, and its behavior is investigated under six different fire scenarios. To analyze the structure under fire loads, the temperature distribution in the members exposed to the fire is first evaluated using the finite element heat transfer analysis method. Using the non-linear time history thermo-mechanics analysis method, the investigated frame is then analyzed, and the displacement and internal forces of the members are obtained. The results of these analyses show that in scenarios where the fire occurs in braced bays, the structure remains stable for a longer time, and the combination of braces and link beams is effective in redistributing the load applied to the adjacent columns.

This study explores how the Fire and Rescue Service can better prepare for solving complex problems in emergencies by using the concept of problems and problem-solving networks. Primary and secondary data from an extensive fire incident were analysed, including semi-structured interviews and incident assessment reports. Complex problems that arise during emergencies can be challenging to define, and solutions can be difficult to identify. However, this study demonstrates that breaking down complex problems into sub-problems can facilitate the identification of what kind of problem-solving network is needed to be able to solve problems in emergencies. Overall, this study contributes to a deeper understanding of the rationale behind problem-solving network in emergency situations and highlights the importance of relationships in problem-solving network to address complex problems during emergencies.

Risk-based design and assessment methods are gaining popularity in performance-based structural fire engineering. These methods usually start by defining a set of hazard scenarios to use as analysis inputs. This approach, proven highly effective for other hazard types such as earthquakes, may not be optimal for fire safety design. Indeed, the strong coupling between the fire phenomenon and structural features enables an ad-hoc design variable selection (and/or optimisation) to reduce fire intensity, making fire scenarios additional design outputs. In addition, such a coupling effect implies that fire scenarios maximising consequences are structure specific. Building on these considerations, this paper discusses the limitations that arise at different analysis steps (i.e., fire-scenario and intensity treatment, identifying fire intensity measures, probabilistic fire hazard analysis, developing fire fragility models, and risk calculation) when using conventional risk-based approaches for design purposes. Furthermore, it compares such approaches with a fire safety design methodology (the Consequence-oriented Fire intensity Optimisation, CFO, approach) that addresses the identified limitations. The potential benefits of integrating the two approaches are also discussed. Finally, the fire design of a simplified steel-girder bridge is introduced as an illustrative example, comparing the consequence metrics and design updating strategies resulting from the two approaches.