Fire

Forest fires alter multiple soil properties, from those related to the carbon cycle to mineralogy; however, the responses of various soils to thermal impact remain unclear. This study examined the impact of fire-induced heating (300, 600, and 900 °C) on the properties of two contrasted soils (Andisol and Inceptisol) with regard to soil organic carbon (SOC), total organic carbon (TOC), dissolved organic carbon (DOC), recalcitrant organic carbon (ROC), soil pH, electrical conductivity (EC), soil water repellency (SWR), soil aggregate stability (SAS), and mineralogy using X-ray diffraction (XRD). SOC and TOC decreased as temperatures increased, with a more pronounced decrease in Andisol (90% loss) than in Inceptisol (80% loss). DOC and SWR peaked at 300 °C but disappeared above 600 °C. Further, ROC increased at 300 °C in both soils, but behaved differently at higher temperatures, remaining stable in Inceptisol and being eliminated in Andisol. Soil pH increased at 600 and 900 °C; meanwhile, EC increased progressively in Andisol but peaked at 300 °C in Inceptisol. SAS remained high in both soils (between 85 and 95%) despite heating. The mineralogical analysis demonstrated how heating induced transformations in iron minerals into more oxidized forms (as hematite and maghemite) in the Andisol, while clay minerals and gibbsite decreased feldspar and quartz accumulation promotion in the Inceptisol. In summary, the initial properties of each soil influenced their respective responses to fire. Full article

Wildfires critically affect ecosystems, carbon cycles, and public health. COVID-19 restrictions provided a unique opportunity to study human activity’s role in wildfire regimes. This study presents a comprehensive evaluation of pandemic-induced wildfire regime changes across global fire-prone regions. Using MODIS data (2010–2022), we analyzed fire patterns during the pandemic (2020–2022) against pre-pandemic baselines. Key findings include: (a) A 22% global decline in wildfire hotspots during 2020–2022 compared to 2015–2019, with the most pronounced reduction occurring in 2022; (b) Contrasting regional trends: reduced fire activity in tropical zones versus intensified burning in boreal regions; (c) Stark national disparities, exemplified by Russia’s net increase of 59,990 hotspots versus Australia’s decrease of 60,380 in 2020; (d) Seasonal shifts characterized by December declines linked to mobility restrictions, while northern summer fires persisted due to climate-driven factors. Notably, although climatic factors predominantly govern fire regimes in northern latitudes, anthropogenic ignition sources such as agricultural burning and accidental fires substantially contribute to both fire incidence and associated emissions. The pandemic period demonstrated that while human activity restrictions reduced ignition sources in tropical regions, fire activity in boreal ecosystems during these years exhibited persistent correlations with climatic variables, reinforcing climate’s pivotal—though not exclusive—role in shaping fire regimes. This underscores the need for integrated wildfire management strategies that address both human and climatic factors through regionally tailored approaches. Future research should explore long-term shifts and adaptive management frameworks. Full article

As the urban underground natural gas pipeline network expands, the explosion risk arising from methane accumulation in drainage ditches due to pipeline leakage has increased severely. A two-dimensional numerical model—9.7 m in length (including a 1-m obstacle section), 0.1 m in diameter, and with a water volume fraction of 0.2—was developed to address the flexible boundary characteristics of urban underground ditches. The investigation examined the influence of methane concentration on explosion propagation characteristics. Results indicated that, at a methane concentration of 11%, the peak pressure attained 157.9 kPa, and the peak temperature exceeded 3100 K—all of which were significantly higher than the corresponding values at 10%, 13%, and 16% concentrations. Explosion-induced water motion exerted a cooling effect that inhibited heat and pressure transfer, while obstacles imposed partial restrictions on flame propagation. Temporal profiles of temperature and pressure exhibited three distinct stages: “initial stability–rapid rise–attenuation”. Notably, at a methane concentration of 16%, the water column formed by fluid vibration demonstrated a pronounced cooling effect, causing faster decreases in measured temperatures and pressures compared to other concentrations. Full article

Melamine formaldehyde particle boards (MFPBs), commonly utilized as a wooden decorative material in traditional architecture, demonstrate considerable performance deterioration with extended age, with reductions in essential flame retardancy and structural integrity presenting substantial risks to fire safety in structures. This research examines the impact of thermo-oxidative aging on the flame retardancy of MFPBs. The morphological evolution, surface composition, and flame-retardant characteristics of aged MFPBs were examined via scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), limiting oxygen index (LOI), and cone calorimeter (CCT). The results indicate that thermo-oxidative aging (60 °C, 1440 h) markedly reduces the activation energy (E, by 17.05%), pre-exponential factor (A, by 68.52%), LOI value (by 4%, from 27.5 to 26.4), and time to ignition (TTI, by 17.1%, from 41 s to 34 s) while augmenting the peak mass loss rate (MHRR, by 4.7%) and peak heat release rate (pHRR, by 20.1%). Subsequent investigation indicates that aging impairs the char layer structure on MFPB surfaces, hastens the migration and degradation of melamine formaldehyde resin (MFR), and alters the dynamic equilibrium between “MFR surface enrichment” and “thermal decomposition”. The identified degradation thresholds and failure mechanisms provide essential parameters for developing aging-resistant fireproof composites, meeting the pressing demands of building safety requirements and sustainable material design. Full article

Frequent wildfires in the eastern grasslands of Mongolia pose significant threats to the ecological environment and pastoral livelihoods, creating an urgent need for high-temporal-resolution and high-precision fire prediction. To address this, this study established a daily-scale grassland fire risk assessment framework integrating multi-source remote sensing data to enhance predictive capabilities in eastern Mongolia. Utilizing fire point data from eastern Mongolia (2012–2022), we fused multiple feature variables and developed and optimized three models: random forest (RF), XGBoost, and deep neural network (DNN). Model performance was enhanced using Bayesian hyperparameter optimization via Optuna. Results indicate that the Bayesian-optimized XGBoost model achieved the best generalization performance, with an overall accuracy of 92.3%. Shapley additive explanations (SHAP) interpretability analysis revealed that daily-scale meteorological factors—daily average relative humidity, daily average wind speed, daily maximum temperature—and the normalized difference vegetation index (NDVI) were consistently among the top four contributing variables across all three models, identifying them as key drivers of fire occurrence. Spatiotemporal validation using historical fire data from 2023 demonstrated that fire points recorded on 8 April and 1 May 2023 fell within areas predicted to have “extremely high” fire risk probability on those respective days. Moreover, points A (117.36° E, 46.70° N) and B (116.34° E, 49.57° N) exhibited the highest number of days classified as “high” or “extremely high” risk during the April/May and September/October periods, consistent with actual fire occurrences. In summary, the integration of multi-source data fusion and Bayesian-optimized machine learning has enabled the first high-precision daily-scale wildfire risk prediction for the eastern Mongolian grasslands, thus providing a scientific foundation and decision-making support for wildfire prevention and control in the region. Full article

In the actual installation of cables, inclined cable laying within covered cable trays is a relatively common method. To investigate the effects of different tilt angles on the combustion behavior of cables within covered cable trays, aluminum conductor polyethylene-insulated power cables were used as the test cables. The flame morphology, temperature distribution, and fire spread rate during the cable combustion process were analyzed for experimental scenarios for which the cable laying angles and the ignition positions changed. The results indicate that the inclination angle of the covered cable tray has a significant impact on flame propagation and temperature distribution. For the ignition located at the lowest part of the cable, the fire spread rate increases significantly with the tilt angle. In contrast, for the ignition located at the highest part of the cable, the fire spread rate initially decreases slightly and then increases, with a relatively smaller overall change in magnitude. Under both ignition positions, the flame spread rate significantly increases at 15–30°. Therefore, in actual cable installation processes, cables within covered troughs should avoid large-angle inclinations. Full article

Due to the unique physicochemical properties of ammonia fuel, any leakages in the engine room will inevitably endanger ship safety. This study focuses on investigating the diffusion behavior of ammonia fuel within the engine room during ship navigation after leakage, aiming to identify hazardous points and implement measures, such as installing air-blowing and extraction devices, to mitigate the risks. To address potential leakage risks in ammonia-fueled ships, a simplified three-dimensional computational model was developed based on ship design drawings and field investigations. ANSYS Fluent software (2024 R2) was employed to simulate ammonia fuel leakage from pipelines and equipment, analyzing the diffusion patterns of leakage at different locations and evaluating the impact of adding air-blowing and extraction devices on leaked fuel in the engine room. The simulation results demonstrate that leakage at point 3 poses the greatest operational hazard, and ammonia fuel leakage during navigation generates combustible gas mixtures within the explosion limit range around the main engine, severely threatening both vessel safety and crew lives. Installing air-blowing and extraction devices in high-risk areas effectively reduces the explosion limit range of ammonia fuel, with air outlet 3 showing optimal mitigation effectiveness against ammonia fuel leakage during ship transportation. Full article

Ensuring proper sizing and fit for U.S. female firefighters’ personal protective clothing and equipment (PPE) is a crucial challenge for researchers and manufacturers. The National Fire Protection Association (NFPA) establishes design and performance standards in the U.S., with NFPA 1977 specifying sizing guidelines for wildland firefighting gear. However, the absence of an anthropometric database representing female firefighters limits the effectiveness of these standards. This research evaluates the effectiveness of NFPA 1977 sizing system by investigating whether correlated body measurements maintain internal consistency and provide data-driven recommendations for improvement. Anthropometric data from 187 U.S. female firefighters were analyzed to assess the 2016 and 2022 NFPA 1977 upper and lower torso sizing systems. Correlation analysis was performed between body measurements and corresponding sizes. Contingency tables presented proportion of participants accommodated. Results indicated significant correlations between chest and wrist measurements and sizes in the upper torso, though these were the only available measurements. In the lower torso, hip size strongly correlated with thigh and knee sizes. However, the system inadequately accommodates female firefighters with larger waist and hip measurements. Furthermore, rise sizes demonstrated inconsistent, weak relationships with hip circumference. Overall, the NFPA 1977 sizing requires revision to better serve U.S. female firefighters. Full article

In the Mediterranean region, the high frequency of fire events is combined with climatic conditions that hinder vegetation recovery. This underscores the urgent need for a post-fire restoration of natural ecosystems and implementation of emergency rehabilitation measures to prevent further degradation. In this study, we investigated the performance of three types of erosion control structures (log dams, log barriers, and wattles), two years after fire, in three Mediterranean areas that were burnt by severe forest fires in 2021. The wooden structures’ ability to infiltrate precipitation was evaluated by 100 infiltration experiments in 25 plots, one and two years after the wildfires. The unsaturated hydraulic conductivity K was determined at two zones formed between consecutive wooden structures, i.e., the erosion zone (EZ) where soil erosion occurs, and the deposition zone (DZ) where the soil sediment is accumulated. These zones showed significant differences concerning their hydraulic behavior, with DZ presenting enhanced infiltration ability by 130 to 300% higher compared to EZ, during both years of measurements. The findings suggest that the implementation of emergency restoration actions after a wildfire can highly affect the burned forest soils’ ability to infiltrate water, preventing surface runoff and erosion, whereas specific structures such as the log dams can be even more effective. Full article

Firefighting is a physically, mentally, and emotionally demanding occupation. These demands are exacerbated by an increase in workload, resulting in an increase in stress and a decrease in recovery. While researchers have examined the influence of workload on stress perceptions, little is known about firefighter perceptions of recovery generally, and no research investigating perceptions of holistic recovery (i.e., physical, mental, and emotional) exists. The purpose of this study was to determine the association between acute workload (i.e., call volume) and firefighter perceptions of stress and recovery from pre-shift to post-shift. Sixteen active-duty firefighters completed the Short Recovery and Stress Scale pre- and post-shift and reported call volume after every shift (N = 156 total shifts). Repeated measures correlations were used to examine the common intraindividual associations between pre- to post-shift perceptions of recovery and stress and call volume. Results indicated that as call volume increased, firefighters perceived themselves to be significantly less recovered overall [r_rm (139) = −0.22, p < 0.001], physically [r_rm (139) = −0.31, p < 0.001], mentally [r_rm (139) = −0.26, p < 0.001], and emotionally [r_rm (139) = −0.27, p < 0.005] and significantly more stressed overall [r_rm (139) = 0.28, p < 0.001], mentally [r_rm (139) = 0.25, p < 0.005], and emotionally [r_rm (139) = 0.21, p = 0.012] post-shift compared to pre-shift. These findings suggest that to optimize firefighter health and well-being, practitioners should monitor call volume and implement appropriate physical, mental, and/or emotional recovery interventions. Full article

This paper investigated the impact of repeated bushfire exposure on the properties of four different types of lightweight aggregate (i.e., expanded perlite, pumice, diatomite and expanded glass) masonry blocks for use in the external walls of bushfire shelters and buildings in bushfire-prone areas. First, the properties of cement, sand and lightweight aggregates were determined. Then, 15 different masonry block cement mixes—control, expanded perlite, pumice, diatomite and expanded glass mixes—were developed using the absolute volume method and lightweight aggregate cement mixes were developed by replacing sand in the control mix with lightweight aggregate on an equal volume basis. The test specimens cast included 100 mm diameter cylinders and 90 mm solid masonry blocks. Prior to bushfire exposure, the density and ambient compressive strength of the cement mixes were determined. Then, masonry blocks were exposed to bushfire flame zone conditions (BAL-FZ) for the first time and then for a second time (i.e., repeated exposure) and the effect of these exposures on the bushfire resistance and compressive strength (i.e., residual strength) of the masonry blocks was examined. The results obtained for the newly developed lightweight aggregate blocks were compared with those of the control block and two different commercially available solid blocks (i.e., Com 1 and Com 2). The control block recorded the highest temperature rises (69 and 84 °C), heating rates (1.26 and 1.47 °C/min) and compressive strength reductions (10.2 MPa) upon first-time and repeated bushfire exposure. The inclusion of lightweight aggregates in the masonry block mix lowered the temperature rises (between 17 and 61 °C) and heating rates (between 1.07 and 0.19 °C/min) on the ambient surface and also resulted in compressive strength reductions (between 3.2 and 9.0 MPa) during first-time and repeated bushfire exposure. Only the diatomite block (D60; block made with 60% diatomite aggregate) and commercial lightweight block (Com 2) remained within the interior temperature limits for bushfire shelters after both the first exposure and repeated exposure. However, only the D60 block satisfied the loadbearing strength requirement of 5 MPa even after repeated exposure. Therefore, considering the need to comply with the temperature limit on the interior surfaces of bushfire shelters during first-time and repeated exposure and to satisfy the loadbearing strength requirement of solid masonry units even after repeated bushfire exposure, the block made with 60% diatomite aggregate is recommended for use in the external walls of buildings in bushfire-prone areas. Full article

This study analyzes forest fire legislation and policies in the Andean Community of Nations (ACN)—Colombia, Ecuador, Peru, and Bolivia—focusing on prevention and control. Using a comparative law approach, similarities, differences, and implementation challenges were identified. Ecuador and Peru have more comprehensive legal structures, while Colombia’s is simpler, and Bolivia falls in between. To address these gaps, this study proposes an Andean Directive for Integrated Fire Management (ADIFM) to harmonize policies and incorporate fire ecology, ancestral knowledge, education, monitoring technologies, and post-fire restoration. This regulatory framework, tailored to Andean ecological and sociocultural conditions, would optimize fire management and strengthen ecosystem resilience. Additionally, harmonizing sanctions and regulations at the regional level would ensure more coherent and effective governance. The ADIFM would provide strategic guidance for policymakers, fostering sustainable fire management and environmental restoration across Andean ecosystems. Full article

Metropolitan city express line tunnels are fully enclosed and often span long distances between stations, allowing multiple trains within a single interval. Traditional segmented ventilation ensures only one train per section, but ultra-long tunnels with shaftless designs introduce new challenges under fire conditions. This study investigates smoke behavior in an ultra-long inter-district tunnel during multi-train blockage scenarios. A numerical model evaluates the effects of train spacing, fire source location, and receding spacing on smoke back-layering, temperature distribution, and flow velocity. Results indicate that when train spacing exceeds 200 m and longitudinal wind speed is above 1.2 m/s, the impact of train spacing on smoke back-layering becomes negligible. Larger train spacing increases back-layering under constant wind speed, while higher wind speeds reduce it. Fire source location and evacuation spacing affect the extent and pattern of smoke spread and high-temperature zones, especially under reverse ventilation conditions. These findings provide quantitative insights into fire-induced smoke dynamics in ultra-long tunnels, offering theoretical support for optimizing ventilation control and evacuation strategies in urban express systems. Full article

The measurement error of sound travel time, one of the most critical parameters in acoustic temperature measurement, is significantly affected by the type of sound source signal. In order to select more appropriate sound source signals, a sound source signal preference study of loose coal acoustic temperature measurement was performed and is described herein. The results showed that the absolute error of the swept signal and the pseudo-random signal both increased with increased acoustic wave propagation distance. The relative error of the swept signal showed a relatively stable upward trend; in comparison, the pseudo-random signal showed a general decrease with a large fluctuation in the middle section, and both the relative and absolute errors for the pseudo-random signal were larger than those of the swept signal. Therefore, the swept signal is expected to perform better than the pseudo-random signal in the loose coal medium. Based on the experimental results, the linear sweep signal was selected as the sound source signal for the loose coal temperature inversion experiments: the average error between the inverted temperature value and the actual value was 4.86%, the maximum temperature difference was 2.926 °C, and the average temperature difference was 1.5949 °C. Full article

The deflagration-to-detonation transition (DDT) is a critical process for achieving reliable ignition in detonation-based propulsion systems, such as Rotating Detonation Engines (RDEs). This study experimentally investigates the effect of spatial variations in blockage ratio (BR) on flame acceleration and detonation onset within a modular pre-detonator. Three DDT device configurations (converging, constant, and diverging) were designed to have an identical average BR of 0.5 and were tested over equivalence ratios ranging from 0.64 to 1.6. High-speed imaging, pressure transducers, and schlieren visualization were employed to characterize flame propagation velocity, pressure evolution, and exit wave structures. The converging configuration consistently promoted earlier detonation onset and higher success rates, especially under fuel-rich conditions (ϕ = 1.6), while the diverging configuration failed to initiate detonation in all cases. Enhanced flame compression in the converging layout led to strong coupling between the shock and reaction fronts, facilitating robust detonation formation. These findings indicate that the spatial distribution of BR, rather than average BR alone, plays a decisive role in DDT performance. This work offers validated design insights for optimizing pre-detonator in RDE applications. Full article

The insulation layer of flame-retardant cables plays a critical role in mitigating fire hazards by influencing toxic gas emissions and the accuracy of fire modeling. This study systematically explores the pyrolysis kinetics and volatile gas evolution of flame-retardant polyvinyl chloride (PVC) and polyethylene (PE) insulation materials using advanced TG-FTIR-GC/MS techniques. Distinct pyrolysis stages were identified through thermogravimetric analysis (TGA) at heating rates of 10–40 K/min, while the KAS model-free method and Málek fitting function quantified activation energies and reaction mechanisms. Results revealed that flame-retardant PVC undergoes two major stages: (1) dehydrochlorination, characterized by the rapid release of HCl and low activation energy, and (2) main-chain scission, producing aromatic compounds that contribute to fire toxicity. In contrast, flame-retardant PE demonstrates a more stable pyrolysis process dominated by random chain scission and the formation of a dense char layer, significantly enhancing its flame-retardant performance. FTIR and GC/MS analyses further highlighted distinct gas evolution behaviors: PVC primarily generates HCl and aromatic hydrocarbons, whereas PE releases olefins and alkanes with significantly lower toxicity. Additionally, the application of a classification and regression tree (CART) model accurately predicted mass loss behavior under various heating rates, achieving exceptional fitting accuracy (R² > 0.98). This study provides critical insights into the pyrolysis mechanisms of flame-retardant cable insulation and offers a robust data framework for optimizing fire modeling and improving material design. Full article

The evolution of a flame front in a channel was considered in a two-dimensional approximation. In the approximation of the potential flow of combustion products and unburned mixture, the formation of a finger-shaped flame was considered after ignition at the closed end of the channel, on the channel axis, and on the side wall of the channel. The prerequisites for the formation of a tulip-shaped flame were considered in a potential approximation. The method of conformal mapping was used. Simple analytical functions were used that allowed equipotential lines and streamlines to be transformed. The shape of the flame front was obtained. The analytical results were compared with the experimentally obtained results of the flame front evolution and with numerical results obtained by other authors. The conditions for the applicability of the conformal mapping to a reacting gas mixture were given. Full article

Applicable recommendations play a key role in improving training and procedures used in civil protection. Since 1 January 2025, the Law on Civil Protection and Civil Defense has been in force in Poland. It responds to the experience of current threats, including the war in Ukraine, the 2024 floods in Western Poland, the COVID-19 pandemic, and other crises. The Act systemically regulates the problem of building social resilience, which must be developed and applied regarding today’s modern threats. The primary actor in civil protection is the fire brigade system, in which volunteer firefighters are recruited from local communities and act for their benefit. In this context, it is interesting to ask whether and what solutions should be applied in order to improve the effectiveness of the training and exercise system of volunteer fire brigades (TSOs) in the field of civil protection and crisis management. The aim of this investigation was to develop evaluations and applicable recommendations to improve the effectiveness of the training system for volunteer firefighters based on a survey of volunteer firefighters in the Cracow Poviat. Two survey diagnostic techniques were used: expert interviews and questionnaire research. The findings were compared with the results of an analysis of source documents obtained in TSO units. The expert interviews covered all chief fire officers of the municipalities in the Cracow Poviat. The paper begins with an introduction and a systematic literature review. The conclusions consist of the proposal of applicable changes in the scope of basic, specialist, and additional training. Areas of missing training are also identified. The firefighters’ knowledge of crisis management procedures is verified, deficiencies are identified, and applicable changes in the organization of field exercises are proposed. Full article

Assessments of subway train fires were conducted based on full-scale experiments and numerical simulations. The experimental platform and simulation model were established according to a real subway train in China. The results show that there was no obvious flame spread, and all the electrical circuitry maintained its integrity during a standard luggage fire. The maximum HRR (heat release rate) of the luggage fire obtained through the full-scale experiment was 155.5 kW, which was almost the same as the standard HRR curve provided in EN 45545-1. However, the fire only lasted approximately 180 s, which was much shorter than a standard fire (600 s). Through numerical simulations of an entire subway train, the side wall and roof ignited quickly, and the fire continually spread to the adjacent compartment under the extreme scenario with a gasoline pool fire and exposed winterproof material. The maximum HRRs of the luggage and gasoline pool fires were 179.7 and 17,800.0 kW, respectively. According to the experimental and simulation results, the Duggan method, which assumes that all combustibles inside a train compartment burn at the same time, was not appropriate for assessing the fires in the subway train, and a simple revised frame was proposed instead. Full article