Fire Technology最新文献

In this paper, a new gram scale experiment with well characterised boundary conditions is proposed for pyrolysis experiments. The set-up consists of a tube furnace, based on ISO19700, with a newly designed concept for a balance within the oven, allowing for online mass loss measurements. Samples with a length up to 50 cm can be investigated in this apparatus. The oven allows for experiments at fixed temperatures or at fixed heating rates, under controlled atmosphere, w.r.t. gas composition and flow rate. A thorough characterisation of the set-up is presented, including aspects like reproducibility of the heating rate or the precision of the balance. The functionality of the balance has been demonstrated with calcium carbonate (CaCO(_{3})) experiments. This material was chosen because it decomposes in a single reaction, which only releases CO(_{2}). This allows for comparison between the mass loss rate of the balance and the CO(_{2}) production rate, measured by a gas analyser. Results for two different heating rates: 3 K/min and 5 K/min and for different masses (25 g and 8.5 g) are presented. The two measurement methods are in excellent agreement. Finally, the data obtained from the new experimental set-up is compared to results from thermogravimetric analyser (TGA) experiments.

Salt solution immersion experiments are crucial for ensuring the safety of lithium-ion batteries during their usage and recycling. This study focused on investigating the impact of immersion time, salt concentration, and state of charge (SOC) on the thermal runaway (TR) fire hazard of 18,650 lithium-ion batteries. The results indicate that corrosion becomes more severe with an increase in immersion time, salt concentration, and SOC. Shorter immersion durations or lower salt concentrations may lead to an increase in the maximum surface temperature of the battery during TR. Within a specific range of immersion time and salt concentration, the immersion can cause TR to happen earlier than usual. Among batteries immersed in a 3.5% NaCl solution for different durations (immersion 2 h in various NaCl concentrations), the earliest instance of TR was observed at a 4 h immersion time (5% immersion concentration). The onset temperature (T_TR) of TR increases with longer immersion times, a higher salt concentration, and a lower SOC, while the total mass loss during TR, as well as the rebound force, decreases. Furthermore, the maximum flame temperature and flame radiant heat flux saw significant reductions after immersion. The rapid decrease in the maximum heat release rate during stable combustion is attributed to the hydrolysis of the electrolyte and the depletion of the electrode active material following the corrosion failure of the safety valve. These findings provide valuable insights into the TR risks to batteries after salt solution immersion.

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.