Fire Technology最新文献

Surface sampling and laboratory analysis for soot/combustion particulates was conducted following a fire at an education/research facility in the southwest United States. This provided a bank of data by which to probabilistically evaluate the behavior of soot loading (counts/mm²) and relative soot concentration (percent ratio; %R) as useful metrics for quantifying differences in soot impact across a building. Surface tape sampling and analysis via light microscopy were conducted via industry standard protocols, and resulting data from various building zones were selected to construct various comparisons. The performance of counts/mm² and %R as metrics to identify differences in soot impact for each comparison was assessed by comparing inference generated by traditional Student’s t test, Mann Whitney U rank comparison (MW), and the directly calculated axiomatic probability associated with difference in detection (pΔf_d). The fourteen (14) comparisons in which a significant difference was inferred via pΔf_d was similarly indicated via Student’s t and/or MW in only four (4) instances. Further, approximately one half of the comparisons generated different inference via pΔf_d for counts/mm² and %R, with the former demonstrating better discriminatory ability. In broad view, the heuristic concept of comparing numerical “soot levels” (e.g., average) by either metric was not generally suitable for the distribution of the data. In contrast, pΔf_d avoids the statistical bias imposed by traditional statistical inference, and ultimately the efficacy of post fire comparative surface sampling is as dependent upon the metric and inference model utilized as it is on the sampling and laboratory analytical protocols.

Densified wood (DW) is a carbon-negative and energy-saving structural material with promising applications in high-rise timber buildings. However, its fire safety issues restrict its applications. In this paper, a bio-material, phytic acid, based flame retardant PPBNOH was prepared to improve the flame retardancy of DW. The structure characteristics, thermal stability, flammability, combustion behavior and mechanical performance of flame-retardant DW (PPBNOH/DW) were studied. Results show that the decomposition of PPBNOH catalyzes char formation and enhances thermal stability. Thus, PPBNOH/DW has a 57% reduced peak mass loss rate and a 27.9% increased char yield. Both the wood dense structure and PPBNOH catalyzation synergistically promote the formation of phosphorus-containing, crosslinked and aromatic char during wood combustion, which hinders heat/mass transfers and enhances flame retardancy. Thus, PPBNOH/DW has a 53.2% limiting oxygen index, a V-0 rating of UL-94 test. It presents delayed ignition time, reduced heat release characteristics and lower heat of combustion (5.37 MJ kg⁻¹) in the cone calorimeter test. BNOH improves the smoke suppression performance of PPBNOH/DW with a 38.6% reduced total smoke production. The compatible and thermally insulating char also enhances the high-temperature heating resistance of PPBNOH/DW as it has the highest remaining mechanical strengths after heating.

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.