Fire, Volume 5, Issue 4 (August 2022) – 40 articles

Despite much research and applications, glass material and its use in buildings is still challenging for engineers due to its inherent brittleness and characteristic features such as sensitivity to stress concentrations, reduction in strength over time and from temperature, and breakage due to the stresses that may build up because of thermal gradients. This paper presents the results of an original test series carried out on monolithic glass panes with the dimensions of 500 × 500 mm² and different thicknesses, under the exposure to radiant heating. The research study also includes a one-dimensional (1D) heat transfer model and a numerical, three-dimensional (3D) thermo-mechanical model that are used to investigate in greater detail the phenomena observed during the experiments. As shown, the behaviour of glass under radiant heating is rather complex and confirms the high vulnerability of this material for building applications. The usability and potential of thermo-mechanical numerical models is discussed towards experimental feedback. Full article

Electrical apparatuses are prone to faults, which generally causes fires. During such fires, the identification of resolidified copper beads on wires has a strong influence on the direction of the fire investigation. There are four kinds of resolidified beads formed on copper conductors that have been through the fire with and without voltage, namely, ‘cause’ beads (CB), ‘victim’ beads (VB), overload globules (OG), and fire melting globules (FG). First, to improve the identification’s objectivity and quantifiability, we used various morphologic parameters of crystals and porosities to express metallurgical microcharacteristics, such as Ar-G, As-G, An-G, Dm-G, R-G, FD-G, Fm-G, Ar-G, As-P, An-P, Dm-P, R-P, FD-P, Fm-P, P3-P, and Cu₂O. Then, several machine learning classifiers were developed to predict the melted beads based on metallurgical morphologic parameters by using SVM, BP neutral network (BPNN), AdaBoost, bagging, and random forest (RF), respectively. Models were trained and tested based on the sample set, consisting of 560 samples which were collected from real room fires. ACC/F1 of the RF model were 0.894/0.805, respectively, which are superior to SVM, BPNN, AdaBoost, and bagging. For the RF classifier, the recall rates of CB, VB, OG, and FG were 92.5%, 67.5%, 100%, and 97.5%, respectively, indicating that RF has best potential to predict OG and FG. The variable importance was analyzed to distinguish key features, and the results revealed that Cu₂O has highest impact on bead classification. We cannot find much promise with this method that uses multiple metallurgical and morphological parameters for distinguishing between CB and VB. It is confirmed that no machine learning classifiers combined with metallurgical analysis could do this work well in this paper. Thus, we strongly recommend that other evidence for investigation in the room fire should also be considered to cover the shortage of this kind. Full article

The study aims to develop a holistic framework for maximum area coverage of a disaster region during a bushfire event. The monitoring and detection of bushfires are essential to assess the extent of damage, its direction of spread, and action to be taken for its containment. Bushfires limit human’s access to gather data to understand the ground situation. Therefore, the application of Unmanned Aerial Vehicles (UAVs) could be a suitable and technically advanced approach to grasp the dynamics of fires and take measures to mitigate them. The study proposes an optimization model for a maximal area coverage of the fire-affected region. The advanced Artificial Bee Colony (ABC) algorithm will be applied to the swarm of drones to capture images and gather data vital for enhancing disaster response. The captured images will facilitate the development of burnt area maps, locating access points to the region, estimating damages, and preventing the further spread of fire. The proposed algorithm showed optimum responses for exploration, exploitation, and estimation of the maximum height of the drones for the coverage of wildfires and it outperformed the benchmarking algorithm. The results showed that area coverage of the affected region was directly proportional to drone height. At a maximum drone height of 121 m, the area coverage was improved by 30%. These results further led to a proposed framework for bushfire relief and rescue missions. The framework is grounded on the ABC algorithm and requires the coordination of the State Emergency Services (SES) for quick and efficient disaster response. Full article

Wildland fire literacy is the capacity for wildland fire professionals to understand and communicate fundamentals of fuel and fire behavior within the socio-ecological elements of the fire regime. While wildland fire literacy is best developed through education, training, and experience in wildland fire science and management, too often, development among early-career professionals is deficient in one or more aspects of full literacy. We report on a hands-on prescribed fire methods workshop designed to provide training and experience in measuring and conducting prescribed fire, with a focus on grassland ecosystems. The workshop was held in March 2022 at The Nature Conservancy’s Dunn Ranch Prairie in northern Missouri. It consisted of hands-on training and experience in measuring fuels, fire weather, and fire behavior. Prescribed fire operations training facilitated both hands-on learning and vicarious learning by rotating squad roles among several small sub-units on the first day of live fire exercises. Participants then gained experience as crew members for two larger prescribed burns (60 and 200 ha). We report here on the successes and lessons learned from the perspectives of both participants and the instructor cadre for what was widely regarded as a successful workshop. Full article

This study aimed to evaluate the egress safety in nursing hospitals based on the capacity of the smoke exhaust system. To this end, the available safe egress time was calculated by analyzing changes in visibility, carbon monoxide, carbon dioxide, oxygen contents, and temperature depending on the fire duration. In addition, an egress simulation was performed using the number of workers (egress guides) and egress delay time as variables, and the required safe egress time was estimated. Based on the results, the egress safety of a prototype nursing hospital was evaluated. In this study, egress safety criteria to evaluate egress safety in a typical nursing hospital were presented, which are expressed in terms of normalized egress guides, the capacity ratio of the smoke exhaust system, and egress delay time. The proposed criteria can be used to evaluate the egress safety of typical nursing hospitals and to prepare complementary measures. Full article

Wildfire is an important natural disturbance agent, shaping mixed conifer forest structure throughout the Southwestern United States. Yet, fire exclusion caused by late 19th century livestock grazing followed by human fire suppression has altered forest structure by increasing forest density, basal area, and canopy cover in recent decades. Changes in the abundance and vertical and horizontal continuity of fuels have increased the potential for high-severity fire, which construes a major regional forest management concern. In May 2016, the Coyote Fire burned through a network of permanent forest monitoring plots in Guadalupe Mountains National Park. This study employed a repeated-measures sampling design to quantify the effects of low- to moderate-severity wildfire on forest stand structure, species composition, fuels, and tree mortality using hierarchical cluster analysis, non-metric multidimensional scaling (nMDS), and paired t-tests. The 2016 Coyote Fire reduced live tree density in small-diameter size classes, but produced minimal changes in canopy stand structure and fuel loadings, despite nearly a century of fire exclusion and pre-fire tree densities that were four-times higher they were prior to last major wildfire in the early 1900s. Small-diameter surface fuel loadings (1 h and 10 h fuels) did not significantly change after fire, although 1000 h fuels increased significantly (p < 0.05), likely from the addition of new fuel from fire-caused tree mortality. While the wildfire reduced live tree density, the nMDS analysis indicated that the wildfire did not trigger major shifts in tree species composition. However, the wildfire triggered significant decreases in seedlings and small-diameter trees (<30 cm DBH) (p < 0.05). Although the fire thinned the forest, the persistence of fuels and increases in dead small-diameter trees heighten the need for additional fuel reduction treatments to mitigate the risk of future high-severity fire under extreme fire weather. Management of low-severity fire in this forest type may provide opportunities to reduce fuels and restore more desirable stand structure to enhance forest resilience to landscape fire. Full article

Forest fires spread via production and combustion of pyrolysis gases in the understory. The goal of the present paper is to understand the spatial location, distribution, and fraction (relative to the overstory) of understory plants, in this case, sparkleberry shrub, namely its degree of understory consumption upon burn, and to search for correlations between the degree of shrub consumption to the composition of emitted pyrolysis gases. Data were collected in situ at seven small experimental prescribed burns at Ft. Jackson, an army base in South Carolina, USA. Using airborne laser scanning (ALS) to map overstory tree crowns and terrestrial laser scanning (TLS) to characterize understory shrub fuel density, both pre- and postburn estimates of sparkleberry coverage were obtained. Sparkleberry clump polygons were manually digitized from a UAV-derived orthoimage of the understory and intersected with the TLS point cloud-derived rasters of pre- and postburn shrub fuel bulk density; these were compared in relation to overstory crown cover as well as to ground truth. Shrub fuel consumption was estimated from the digitized images; sparkleberry clump distributions were generally found to not correlate well to the overstory tree crowns, suggesting it is shade-tolerant. Moreover, no relationship was found between the magnitude of the fuel consumption and the chemical composition of pyrolysis gases, even though mixing ratios of 25 individual gases were measured. Full article

The methodology used by the First Street Foundation Wildfire Model (FSF-WFM) to compute estimates of the 30-year, climate-adjusted aggregate wildfire hazard for the contiguous United States at 30 m horizontal resolution is presented. The FSF-WFM integrates several existing methods from the wildfire science community and implements computationally efficient and scalable modeling techniques to allow for new high-resolution, CONUS-wide hazard generation. Burn probability, flame length, and ember spread for the years 2022 and 2052 are computed from two ten-year representative Monte Carlo simulations of wildfire behavior, utilizing augmented LANDFIRE fuel estimates updated with all the available disturbance information. FSF-WFM utilizes ELMFIRE, an open-source, Rothermel-based wildfire behavior model, and multiple US Federal Government open data sources to drive the simulations. LANDFIRE non-burnable fuel classes within the wildland–urban interface (WUI) are replaced with fuel estimates from machine-learning models, trained on data from historical fires, to allow the propagation of wildfire through the WUI in the model. Historical wildfire ignition locations and NOAA’s hourly time series of surface weather at 2.5 km resolution are used to drive ELMFIRE to produce wildfire hazards representative of the 2022 and 2052 conditions at 30 m resolution, with the future weather conditions scaled to the IPCC CMIP5 RCP4.5 model ensemble predictions. Winds and vegetation were held constant between the 2022 and 2052 simulations, and climate change’s impacts on the future fuel conditions are the main contributors to the changes observed in the 2052 results. Non-zero wildfire exposure is estimated for 71.8 million out of 140 million properties across CONUS. Climate change impacts add another 11% properties to this non-zero exposure class over the next 30 years, with much of this change observed in the forested areas east of the Mississippi River. “Major” aggregate wildfire exposure of greater than 6% over the 30-year analysis period from 2022 to 2052 is estimated for 10.2 million properties. The FSF-WFM represents a notable contribution to the ability to produce property-specific, climate-adjusted wildfire risk assessments in the US. Full article

This paper presents work on investigating the effect of the initial size of water mist droplets on the evaporation and removal of heat from the fire-induced hot gas layer while travelling through the air in a compartment. The histories of the temperature, diameter and position of droplets with different initial diameters (varied from 100 µm to 1000 µm) are determined considering surrounding air temperatures of 75 °C and 150 °C and a room height of 3.0 m. A water droplet evaporation model (WDEM) developed in a previous study (Fire and Materials 2016; 40:190–205) is employed to navigate this work. The study reveals that tiny droplets (for example, 100 µm) have disappeared within a very short time due to evaporation and travelled a very small distance from the spray nozzle because of their tiny size. In contrast, droplets with a larger diameter (for example, 1000 µm) reached the floor with much less evaporation. In the case of this study, the relative tiny droplets (≤200 µm) have absorbed the highest amount of energy from their surroundings due to their complete evaporation, whereas the larger droplets have extracted less energy due to their smaller area/volume ratios, and their traverse times are shorter. One of the key findings of this study is that the smaller droplets of spray effectively cool the environment due to their rapid evaporation and extraction of heat from the surroundings, and the larger droplets are effective in traversing the hot air or smoke layer and reaching the floor of the compartment in a fire environment. The findings of this study might help in understanding the behaviour of water-mist droplets with different initial diameters in designing a water-mist nozzle. Full article

Mediterranean Basin forest ecosystems are recurrently affected by wildfires. The occurrence of insect pests following fire may be a critical factor affecting tree survival and forest recovery. Although ambrosia beetles are viewed with increasing concern, information about the host selection and colonization behavior of these beetles in Mediterranean broadleaf forests is very scarce and inexistent in areas affected by wildfires. After a forest fire in Portugal, we selected 841 burned and unburned cork oak trees and assessed the presence and intensity of ambrosia beetle attacks, as well as other tree characteristics, and used generalized linear models to investigate the factors driving host selection. In contrast with burned oaks, where beetle attacks were frequent, the unburned trees were little affected. Attacks in the burned forest were more frequent in larger trees that suffered higher fire severity, in trees being exploited for cork (but with thicker bark), and in trees that were closer to the unburned area. A contagious effect to neighboring unburned trees was not observed, and cork harvesting in subsequent years following fire also did not increase the probability of beetle attacks. These results help us to understand the risk of ambrosia beetle attacks and improve forest management in cork oak forests. Full article

The numerical simulation method is used to simulate the distribution characteristics of the smoke temperature field of a double-deck bridge smoke temperature field during tanker fire under natural ventilation. The influence of the distance between double decks on the truss and ceiling temperature field change in the double-deck bridge is investigated. The results show that the range of high-temperature area gradually decreases with the increase in bridge deck spacing. The maximum excess temperature function of the tunnel ceiling is also applicable to the bridge, but the coefficient is smaller than that of the tunnel experimental formula. An equation is proposed to predict the maximum excess temperature of the truss under different bridge deck spacings. As the bridge deck spacing increases, the maximum excess temperature decreases. The excess temperature of the truss increases along the truss, and the maximum excess temperature appears at the top of the truss. Based on the energy equation, an equation for the excess temperature of the truss is established. As the vertical height increases, the excess temperature of the truss above the fire source exponentially increases. The research results will contribute to the fire hazard evaluation and safety design of bridges. Full article

While developing a standard for the determination of safety characteristics for hybrid mixtures the authors discovered, that, beside the ignition source, the mixing procedure is the main difference between the single-phase standards for dusts and gases. The preparation of hybrid mixtures containing a flammable gas and a flammable dust in the 20 L-sphere can be realized in different ways. Either the flammable gas is filled only in the sphere or only in the dust container or in both. In previous works, almost always the first method is applied, without giving any information on the accuracy of the gas mixtures. In this work the accuracy of the gas mixtures and the results of the tests applying two methods of mixing were studied. No significant influence of the mixing method itself on the safety characteristics explosion pressure p_ex and the normalized rate of pressure rise (K-value) was found. Obviously, homogenization of the gas mixtures can be obtained sufficiently by the turbulence that is caused during the injection from the dust container into the explosion chamber within a short time. However, the mixing procedure has a great influence on the accuracy of the gas amount of the mixtures obtained. Without modifying the 20 L-sphere by installing precise pressure sensors, assuring its tightness and performing gas analysis, it must be expected, that the accuracy of the gas mixtures is very low. This has a significant influence on the measured safety characteristics and may lead to unsafe facilities or unnecessary expensive safety measures. Full article

Elucidating the characteristics of continuous oil spill fires for different slope conditions can provide important theoretical support for the prevention of, and rescue strategies during, oil spill fire accidents. For this research, we conducted experiments to observe the spread and burning process of continuous oil spill fires under different slope conditions. The changes in physical attributes, such as flame spread rate, burning rate, heat convection at the bottom surface, and flame feedback radiation, were analyzed for the different slope conditions. The results showed that the shrinking phase becomes difficult to see, and the steady phase disappears when the slope increases in the spread and burning process. When the slope increases, the spread speed and spread area increase, and burning rate decreases. Compared with a non-burning process, the resistance to spread decreases in the burning process. We show that the slope directly affects the spreading process, and indirectly affects the burning process. Full article

Very few multi-species or ecosystem comparisons of post-fire vertebrate herbivore activity and food preference exist to inform fire management and conservation strategies. We inferred post-fire (1–3 years) native and introduced vertebrate herbivore activity and attraction to six diverse temperate vegetation communities (grassland to rainforest) from scat counts. We hypothesised that where fire reduced herbaceous and grassy vegetation (‘fodder’), vertebrate herbivores would decline, and that post-fire preferences of native versus exotic herbivores would differ significantly. Instead, we found evidence for a ‘fire and fodder reversal phenomenon’ whereby native macropod and exotic deer scats were more abundant after fire in consistently ‘fodder-poor’ vegetation types (e.g., heath) but less abundant after fire in previously fodder-rich vegetation communities (e.g., grassland). Fodder cover predicted native macropod, wombat, and introduced deer activity and bare ground cover was strongly associated with introduced herbivore activity only, with the latter indicating post-fire competition for food sources due to their abundance in high-altitude open ecosystems. We, therefore, found environmental and vegetation predictors for each individual species/group and suggest broadscale multi-environment, multispecies observations to be informative for conservation management in potentially overlapping post-fire niches. Full article

In seasonally dry environments, the amount of water held in living plant tissue—live fuel moisture (LFM)—is central to vegetation flammability. LFM-driven changes in wildfire size and frequency are particularly important throughout southern California shrublands, which typically produce intense, rapidly spreading wildfires. However, the relationship between spatiotemporal variation in LFM and resulting long-term regional patterns in wildfire size and frequency within these shrublands is less understood. In this study, we demonstrated a novel method for forecasting the LFM of a critical fuel component throughout southern California chaparral, Adenostema fasciculatum (chamise) using gridded climate data. We then leveraged these forecasts to evaluate the historical relationships of LFM to wildfire size and frequency across chamise-dominant California shrublands. We determined that chamise LFM is strongly associated with fire extent, size, and frequency throughout southern California shrublands, and that LFM–wildfire relationships exhibit different thresholds across three distinct LFM domains. Additionally, the cumulative burned area and number of fires increased dramatically when LFM fell below 62%. These results demonstrate that LFM mediates multiple aspects of regional wildfire dynamics, and can be predicted with sufficient accuracy to capture these dynamics. Furthermore, we identified three distinct LFM ‘domains’ that were characterized by different frequencies of ignition and spread. These domains are broadly consistent with the management thresholds currently used in identifying periods of fire danger. Full article

A significant amount of research has been conducted on the resource allocation in fire departments (RAFD) and literature reviews about the fire protection service (FPS), but to the best of our knowledge, no literature reviews have been conducted about the RAFD. Therefore, the purpose of this research is to review literature about allocating resources to urban fire departments (FDs) to gain state-of-the-art knowledge of RAFD and identify the most frequent methodologies and measures in the studies. A five-stage structured literature review (SLR) is undertaken to analyze the RAFD-related studies; subsequently, statistical analysis is used to disclose additional information from the retrieved data and develop a general framework for RAFD. According to the structured literature review, which yielded 417 independent variables for RAFD, integer programming (IP) and data envelopment analysis (DEA) are the most common approaches for RAFD among the mathematical and statistical models in the evaluated articles. Based on the findings, a general conceptual framework for RAFD is suggested. The findings of this study can help public and private FDs and FPS managers, decision-makers, resource allocation (RA) researchers, and academicians gain state-of-the-art knowledge of RAFD. The proposed RAFD framework can provide the FPS decision-makers with the appropriate method and variables for allocating their limited resources in a more efficient way within their FDs. Full article

This study sought an effective detection method not only for flame but also for the smoke generated in the event of a fire. To this end, the flame region was pre-processed using the color conversion and corner detection method, and the smoke region could be detected using the dark channel prior and optical flow. This eliminates unnecessary background regions and allows selection of fire-related regions. Where there was a pre-processed region of interest, inference was conducted using a deep-learning-based convolutional neural network (CNN) to accurately determine whether it was a flame or smoke. Through this approach, the detection accuracy is improved by 5.5% for flame and 6% for smoke compared to when a fire is detected through the object detection model without separate pre-processing. Full article

Combustible decks are identified as vulnerable components of buildings in wildfire-prone areas. In California, combustible deck boards can comply with the requirements of Chapter 7A of the California Building Code if they pass an under-deck flame-impingement exposure test. It is desirable if standard test methods can simplify procedures while not adversely affecting the reliability of the test. The test methods should also be able to discriminate the fire performance between products on the market. In this research, the specified conditions in the under-deck flame-impingement test, SFM 12-7A-4A and ASTM E2632, were evaluated. Different deck assemblies were exposed to above-deck ember and under-deck flame-impingement exposures. During the above-deck ember exposure tests, it was observed that embers accumulated in the gaps between deck boards, on top of the support joists, and, when ignition occurred, ignited in this area. Flames spread by burning into unburned areas of the deck boards and joists, thereby providing a pathway to the building. During the under-deck flame-impingement tests, the three assumptions in the standard test method were evaluated, namely, (1) a small deck size can adequately represent the performance of larger decks, (2) the absence of wind will not noticeably influence performance, and (3) differences in joist material would not noticeably change the performance of the deck boards. Results of experiments suggested that the current Chapter 7A compliant deck boards burned intensely and exposed the cladding of the test building, resulting in an elevated temperature at the wall. It is argued that the current assumptions are an oversimplification of real-world fire performance and a change in the current California’s building code is necessary. This research demonstrated the necessity of evaluating an entire deck assembly rather than only the walking surfaces. Full article

Wildfires are increasingly understood as an ecological driver within the entire Arctic biome. Arctic soils naturally store large quantities of C, as peat has formed throughout the Holocene. For the Siberian Arctic, we used observations from the MODIS remote sensing instrument to document changes in frequency, geographic extent, and seasonal timing of wildfires as well as vegetation productivity (GPP, NPP, EVI). We also used correlation and regression analysis to identify environmental factors of temperature, precipitation, and lightning occurrence associated with these changes. For the Siberian Arctic as a whole, we found that the decadal frequency of wildfire tripled from the 2001–2010 to the 2011–2020 periods. Increased decadal frequency was accompanied by the increased extent of the burnt area by a factor of 2.6. This increase in fire frequency and extent was not uniform, with the greatest increase in western Siberia with no marked increase for the Siberian Far East. These changes were accompanied by the northward migration of the northern limit of wildfire occurrence and an increase in duration of the wildfire season. We found that annual fire frequency and the extent of burnt areas were related to various combinations of seasonal air temperature, precipitation, ground moisture, and lightning frequency. After fires, vegetation productivity rapidly recovered to pre-fire levels. The northward spread of wildfire into the tundra will release carbon long-stored as peat. The enhanced vegetation productivity, rapid recovery of carbon fixation for burnt areas and the northward migration of boreal forest tree species may offset that release and maintain the current status of the Siberian Arctic as a C sink. Increased wildfire and loss of permafrost may threaten ongoing settlement and industrialization, particularly for western Siberia. Full article

Polyurethane material is used as an interior finish and wall cavity insulation. Flame-retardant products may be used for ignition, flame diffusion, and heat-release blocking. A large-scale test was conducted to understand the flame propagation characteristics of polyurethane with the addition of a flame retardant. The fire propagation properties and fire risks of four commonly used polyurethane materials were examined using three tests. Specifically, ignition properties, flame propagation behavior, and flashover occurrence were probed using full-scale tests, while heat release and fire characteristics were examined using cone calorimeter tests, and the toxicity of gaseous combustion products was assessed using gas toxicity tests. PIR F and PIR B, which contained flame retardants, featured slow flame propagation and a long-lasting residual flame, and PIR F released HCl and Br₂ on combustion. Full-scale tests revealed that although external flame propagation was always accompanied by flashover, irrespective of whether the flame retardant was present, a delay or blockage of energy transfer to the inside was observed for flame-retardant-containing specimens. Apart from checking the safety at the material level, the importance of identifying the actual fire characteristics through a full-scale test was confirmed. Full article

Wildfires are not only a natural part of many ecosystems, but they can also have disastrous consequences for humans, including in Australia. Rugged terrain adds to the difficulty of predicting fire behavior and fire spread, as fires often propagate contrary to expectations. Even though fire models generally incorporate weather, fuels, and topography, which are important factors affecting fire behavior, they usually only consider the surface wind; however, the more elevated winds should also be accounted for, in addition to surface winds, when predicting fire spread in rugged terrain because valley winds are often dynamically altered by the interaction of a layered atmosphere and the topography. Here, fire spread in rugged terrain was examined in a case study of the Riveaux Road Fire, which was ignited by multiple lightning strikes in January 2019 in southern Tasmania, Australia and burnt approximately 637.19 km². Firstly, the number of conducive wind structures, which are defined as the combination of wind and temperature layers likely to result in enhanced surface wind, were counted by examining the vertical wind structure of the atmosphere, and the potential for above-surface winds to affect fire propagation was identified. Then, the multiple fire propagations were simulated using a new fire simulator (Prototype 2) motivated by the draft specification of the forthcoming new fire danger rating system, the Australian Fire Danger Rating System (AFDRS). Simulations were performed with one experiment group utilizing wind fields that included upper-air interactions, and two control groups that utilized downscaled wind from a model that only incorporated surface winds, to identify the impact of upper air interactions. Consequently, a detailed analysis showed that more conducive structures were commonly observed in the rugged terrain than in the other topography. In addition, the simulation of the experiment group performed better in predicting fire spread than those of the control groups in rugged terrain. In contrast, the control groups based on the downscaled surface wind model performed well in less rugged terrain. These results suggest that not only surface winds but also the higher altitude winds above the surface are required to be considered, especially in rugged terrain. Full article

This paper presents equations for fuel load and fuel hazard rating (FHR) models based on the time since last fire for dry eucalypt forests in eastern Tasmania. The fuel load equations predict the load of the surface/near-surface and elevated fine fuel. The FHR equations predict the surface, near-surface, combined surface and near-surface, bark, and overall FHR. The utility of the “Overall fuel hazard assessment guide” from Victoria, Australia, is assessed for Tasmanian dry eucalypt forests: we conclude that, when fuel strata components are weighted according to their influence on fire behaviour, the Victorian guide provides a rapid, robust, and effective methodology for estimating FHR. The equations in this paper will be used for operational planning and on-the-ground performing of hazard reduction burning, prediction of fire behaviour for fire risk assessments and bushfire control, and providing inputs into the new Australian Fire Danger Rating System. Full article

Longitudinal ventilation fans in extra-long submarine tunnels are usually arranged at both ends of the tunnel limited by the tunnel cross section, which is usually hindered by insufficient power caused by extra-long ventilation distances. In this paper, the conception of a ventilation mode is proposed that services the tunnel and cross passages, to provide auxiliary air supply to the main tunnel. Two critical factors have been analyzed on the premise of evacuation safety, which combine to affect the ventilation efficiency in the case of an accident inside the tunnel, these are: air volume within the service tunnel, and cross passage open numbers. FDS simulation software is used to simulate the tunnel model; consider the number of cross passages from one to four; and simulate the service tunnel airflow velocity of 0.7 m/s, 0.75 m/s, 0.85 m/s, 1.0 m/s and 1.3 m/s. The results show that when 1.3 m/s wind speed is applied at both ends of the service tunnel, and three cross passages are operated, 20 MW of fire smoke within the accident tunnel can be effectively controlled; additionally, the wind speed in the cross passage will not hinder the evacuation. The simulation results are verified by ventilation network calculation. Full article

In this study, a series of numerical simulations were carried out to investigate the effect of fire shutter descending height on the smoke extraction efficiency in a large space atrium. Based on the full-scale fire experiments, this paper carried out more numerical simulations to explore factors affecting the smoke extraction efficiency in the atrium. The smoke flow characteristics, temperature distribution law and smoke extraction efficiency of natural and mechanical smoke exhaust systems were discussed under different heat release rates and fire shutter descending heights. The results show that the smoke spread rate and the average temperature of the smoke are higher with a greater heat release rate. After the mechanical smoke exhaust system is activated, the smoke layer thickness and smoke temperature decrease, and the stable period of heat release rate is shorter. In the condition of natural smoke exhaust, the smoke extraction efficiency increases exponentially with the increase of heat release rate and the descending height of the fire shutter, and the maximum smoke extraction efficiency is 48.8%. In the condition of mechanical smoke exhaust, the smoke extraction efficiency increases with the increase of mechanical exhaust velocity. When the velocity increases to the critical value (8 m/s), the smoke extraction efficiency is essentially stable. The smoke extraction efficiency is increased first with the increase of fire shutter descending height and then has a downward trend when the descending height drops to half, and the maximum smoke extraction efficiency is 70.3% in the condition of mechanical smoke exhaust. Empirical correlations between the smoke extraction efficiency and the dimensionless fire shutter descending height, the dimensionless heat release rate and the dimensionless smoke exhaust velocity have been established. The results of this study can provide a reference for the design of smoke prevention and exhaust systems in the atrium. Full article

Fires can alter the hydraulic properties of burned soils through the consumption of organic matter on the ground surface. This study examined the effects of rainfall on the presence of soil pore clogging with varying ash layer thickness using laboratory rainfall simulator experiments. The image analysis with resin impregnation showed that rainfall impact caused plugging of soil pores at 22.2% with soil particles and 14.3% with ash particles on near surface soils (0–5 mm below). High rainfall intensities enhanced soil pore clogging by ash particles, particularly at shallow soil depths (0–10 mm). Ash deposits on the soil surface increased the water-absorbing capacity of ash-covered soils compared with that of bare soils. The rainfall simulation experiments also showed that ash cover led to a reduction in soil hydraulic conductivity, owing to the combined effects of surface crust formation and soil pore clogging. The complementary effects of soil pore clogging and water absorption by ash cover could hamper the accurate understanding of the soil hydrologic processes in burned soils. Full article

The island of Madagascar, located in the southern hemisphere between the equator and the Tropic of Capricorn in the Indian Ocean, 450 km from the African continent, is particularly affected by wildfires. The vegetation of the phytogeographic Western Domain of the island consists largely of savannas, wooded grassland, and secondary grassland, maintained by the repeated action of fire operating each year on a seasonal cycle. Rural populations employ fire to manage land use. Depending on the burning practice and the environment in which the fires happen, the impacts vary. This paper supplement the studies that have so far located and quantified wildfires by taking into account their different behaviors, particularly their spread. We analyzed the modalities of the relationship between the two fire products, active fire and burned area, derived from Moderate Resolution Imaging Spectroradiometer (MODIS) data to establish a typology based on fire spread patterns. We identified three general patterns of fire behaviors, as well as their locations in the studied area. Spatial analysis of this patterns enabled us to understand spatial logics better. Type 1 fires are the least frequently observed and have many active fires, but little or no burned area. Type 2 fires are the most common and have areas that burn like a mosaic. Type 3 fires are observed slightly less frequently than the previous type and have few active fires and large burned areas. An inter-annual analysis reveals the spatial stability or variability of these fire types. Full article

Window sprinklers are commonly used to protect glass, but there is a lack of research on the effect of fire scale on protection. In this study, full-scale experiments on sprinkler-protected glass in building fires were carried out. The experimental process was simulated using CFD numerical simulation software (FDS), and the effect of the heat release rate on the protection effect was revealed based on the glass surface temperature and heat insulation efficiency. It was found that in a full-size compartment fire, the window sprinkler was able to protect the glass from being damaged by high-temperature smoke. The numerical simulation could effectively simulate the spray distribution pattern of a window sprinkler as well as the gas temperature evolution, and the simulation results matched well with the full-size experiments. The window surface temperatures all decreased rapidly and increased linearly with the HRR after the window sprinkler was activated. The steady-state window center temperatures were 40 °C, 60 °C and 76 °C when the HRR was 2 MW, 4 MW and 6 MW, respectively. The window center temperature was less than the critical temperature of glass breakage, indicating that the window sprinkler could protect the glass from fire damage well, within the fire scale of 6 MW. The thermal insulation efficiency in the edge region was slightly lower than that in the center of the window. In the range of 2 to 6 MW, there was no significant correlation between the thermal insulation efficiency and the HRR, and the thermal insulation efficiency was in the range of 54% to 59%. Full article

The flow and dispersion characteristics of the fire extinguishing agent in the pipings and the concentration distribution in the nacelle are essential for optimizing the aircraft fire extinguishing system. In the present work, we developed a three-dimensional CFD model to simulate the transport and dispersion of the agent in piping and nacelle. The results show that the length and structure of the pipings near the nozzles affect the concentration, pressure, flow rate, and flow distribution of the extinguishing agent. The smaller the bend of the pipings near the nozzles and the angle of connection with the main piping, the less time it takes for the agent to reach the nozzles and the more mass flow rate of the agent is injected, which is more conducive to extinguishing fire rapidly. External ventilation and the blockage of the nacelle’s ribs and other components impact the concentration distribution of the fire extinguishing agent in the nacelle. The agent is mainly concentrated in the middle and rear areas of the engine nacelle. Agent concentration tests were carried out in the simulated engine nacelle. The experimental result is similar to the simulation result, which verifies the feasibility of the simulation method. The simulation method can be used to increase the concentration of fire extinguishing agent to meet the safety requirements by changing the outside ventilation and increasing the filling amount of fire extinguishing agent, so as to achieve the optimization of the fire extinguishing system. Full article

Lightning is the main precursor of wildfires in Arizona, New Mexico, and Florida during the fire season. Forecasting the occurrence of Lightning-Ignited Wildfires (LIW) is an essential tool to reduce their impacts on the environment and society. Long-Continuing-Current (LCC) lightning is proposed to be the main precursor of LIW. The long-lasting continuing current phase of LCC lightning is that which is more likely to ignite vegetation. We investigated the meteorological conditions and vegetation type associated with LIW and LCC lightning flashes in Arizona, New Mexico, and Florida. We analyzed LIW between 2009 and 2013 and LCC lightning between 1998 and 2014 and combined lightning and meteorological data from a reanalysis data set. According to our results, LIW tend to occur during dry thunderstorms with a high surface temperature and a high temperature gradient between the 700 hPa and the 450 hPa vertical levels for high-based clouds. In turn, we obtained a high lightning-ignition efficiency in coniferous forests, such as the ponderosa pine in Arizona and New Mexico and the slash pine in Florida. We found that the meteorological conditions that favor fire ignition and spread are more significant in Florida than in Arizona and New Mexico, while the meteorological conditions that favor the occurrence of LIW in Arizona and New Mexico are closely related with the meteorological conditions that favor high lightning activity. In turn, our results indicate high atmospheric instability during the occurrence of LIW. Our findings suggest that LCC (>18 ms) lightning tends to occur in thunderstorms with high relative humidity and ice content in the clouds, and with low temperature in the entire troposphere. Additionally, a weak updraft in the lower troposphere and a strong one in the upper troposphere favor the occurrence of LCC (>18 ms) lightning. We found that the meteorological conditions that favor the occurrence of LCC (>18 ms) lightning are not necessarily the preferential meteorological conditions for LIW. Full article

In recent decades, wildfires in many areas of the United States (U.S.) have become larger and more frequent with increasing anthropogenic pressure, including interactions between climate, land-use change, and human ignitions. We aimed to characterize the spatiotemporal patterns of contemporary fire characteristics across the contiguous United States (CONUS). We derived fire variables based on frequency, fire radiative power (FRP), event size, burned area, and season length from satellite-derived fire products and a government records database on a 50 km grid (1984–2020). We used k-means clustering to create a hierarchical classification scheme of areas with relatively homogeneous fire characteristics, or modern ‘pyromes,’ and report on the model with eight major pyromes. Human ignition pressure provides a key explanation for the East-West patterns of fire characteristics. Human-dominated pyromes (85% mean anthropogenic ignitions), with moderate fire size, area burned, and intensity, covered 59% of CONUS, primarily in the East and East Central. Physically dominated pyromes (47% mean anthropogenic ignitions) characterized by relatively large (average 439 mean annual ha per 50 km pixel) and intense (average 75 mean annual megawatts/pixel) fires occurred in 14% of CONUS, primarily in the West and West Central. The percent of anthropogenic ignitions increased over time in all pyromes (0.5–1.7% annually). Higher fire frequency was related to smaller events and lower FRP, and these relationships were moderated by vegetation, climate, and ignition type. Notably, a spatial mismatch between our derived modern pyromes and both ecoregions and historical fire regimes suggests other major drivers for modern U.S. fire patterns than vegetation-based classification systems. This effort to delineate modern U.S. pyromes based on fire observations provides a national-scale framework of contemporary fire regions and may help elucidate patterns of change in an uncertain future. Full article