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2024 | Book

Wood & Fire Safety 2024

Proceedings of the 10th International Conference on Wood & Fire Safety 2024

Editors: Linda Makovická Osvaldová, Laura E. Hasburgh, Oisik Das

Publisher: Springer Nature Switzerland


About this book

This proceedings volume presents new scientific works of the research workers and experts in the field of Wood Science & Fire.
It looks into the properties of various tree species across the continents affecting the fire-technical properties of wood and wood-based materials, its modifications, fire-retardant methods and other technological processes that have an impact on wood ignition and burning. The results of these findings have a direct impact on Building Construction and Design describing the fire safety of wooden buildings, mainly large and multi-story ones. The results of these experiments and findings may be applied, or are directly implemented into Fire Science, Hazard Control, Building Safety which makes the application of wood and wood materials in buildings possible, while maintaining strict fire regulations.
One part of the contributions focuses on the symbiosis of the material and the fire-fighting technologies. Wood burning has its own specific features, therefore, the fire protection technologies need to be updated regularly. It also includes the issue of the intervention of fire-fighting and rescue teams in the fires of wooden buildings. Presentations deal with the issue of forest fires influenced by the climate changes, relief, fuel models based on the type and the age of the forest stand.

Table of Contents


Structure and Properties of Wood and Its Changes at High Temperatures

Nanostructural Cell Wall Changes Due to Thermal Degradation in Wood

Pyrolysis of wood involves the thermal degradation of the wood polymers and the formation of char. Understanding how char forms, particularly, in terms of the nano-structural changes that take place during pyrolysis will inform fire models to ensure fire safety in timber structures. Here, small- and wide-angle x-ray scattering (SAXS/WAXS) based tomography were used to study how thermal degradation changes wood nanostructure across the pyrolysis zone in Douglas-fir. The changes in the aggregation of cellulose elementary fibrils (via SAXS) as well as changes in the cellulose crystallinity (via WAXS) were measured. Tomographic reconstructions from the scattering contrast and absorption data were computed to visualize and quantify these changes across the entire cellular structure of the samples. Preliminary results revealed relatively abrupt changes in the cellulose crystallinity as the wood polymers are thermally degraded. With SAXS we observed changes in the overall intensity as a function of thermal degradation, which suggests that the packing of the elementary fibrils may be modified as some of the polymers are degraded.

Nayomi Z. Plaza, Laura E. Hasburgh, Lin Yang, Nathan J. Bechle
Determination of Notional Char Rates for Protected and Unprotected Timber When Subjected to Variations in Heating Regimes, Test Duration and Thermocouple Configurations

There has been much discussion in technical literature regarding the best method of installing thermocouples to minimise interference with the specimen, ensure accurate thermocouple positioning, minimise errors if the thermocouple cables are not run continuously along isotherms as well as the selection of the construction of thermocouples. Consensus is difficult to achieve given the best method will tend to vary depending upon the application and a broad range of fixing techniques, configurations and thermocouple types that have been used in standard and enclosure fires which complicates the application of data from multiple sources. To investigate these variations, a test program to systematically quantify the performance of timber construction under a range of simulated fire conditions has been undertaken to provide a better understanding to the sensitivity of timbers to variations in heating regimes.The test series compared a proposed alternative configuration using ceramic fibre insulation and screwing adjacent timber sections together without the use of adhesives, to that of the proposed European configuration requiring rebating of the timber sections to run thermocouple leads and bonding of timber members together. The tests were performed using the standard and hydrocarbon heating regimes and different thermocouple configurations were evaluated to quantify potential variations that can occur. The tests also quantified variations in the measured char rates with different heating regimes, different exposure times for protected and unprotected timber, and enable char rate modifications to be derived to account for these variables.

Paul England, Boris Iskra
Reaction to Fire of Eight Species of Densified Mexican Wood

The objective of the research was to evaluate the ignition time and mass loss in fire reaction tests of eight species of densified Mexican wood. A 30% densification coefficient was applied. For each species, two samples of densified and non-densified wood were contrasted in ad-hoc reaction to fire tests for the investigation. The fire exposure time of five minutes was sufficient to reach the ignition time of the specimens and cause a loss of mass. Wood densification is a treatment that increases the ignition time and decreases mass loss when wood is exposed to fire under laboratory conditions. The magnitudes of ignition time and mass loss are different for each species. There is no clear statistical trend in mass loss as a function of densification. Prospectively, the eight species of wood investigated are potential candidates for densification treatment in order to improve their properties of wood density and reaction to fire.

Javier Ramón Sotomayor Castellanos, Koji Adachi, Linda Makovická Osvaldová
Numerical Analysis of Cross-Laminated Timber (CLT) Wall Panels Under Fire

Cross-laminated timber (CLT) has gained popularity worldwide as a sustainable building product, attracting the attention of designers, engineers, and builders in recent years. However, the behaviour of timber under fire is a significant concern because of its combustible nature. Only limited research has been conducted on the fire behaviour of CLT using finite element (FE) analysis. The main aim of this study is to develop an FE model to investigate the behaviour of CLT wall panels under exposure to standard fire conditions. The accuracy of the FE model was validated by comparing the experimental results of the temperature distribution at different thickness depths of the CLT panels obtained from the literature, with the predicted results from the numerical analysis. Furthermore, a comparative analysis was performed to establish the fire resistance, charring rate, and charred depth of different CLT panels, and the outcome was compared with the experimental results. The predicted temperatures within the CLT panels from the FE model were observed to be in good agreement with the experimental results under fire exposure, which may reduce the number of necessary lab experiments in the future.

Muhammad Yasir, Kieran Ruane, Vesna Jaksic
The Method of Interpolation of the Charred Zone in the Cross-Section of Wooden Beams with Fire-Resistant Cladding Based on Impregnated Plywood

This article discusses the developed method of interpolation of the charring zone in cross-sections of wooden beams with fire-resistant cladding based on impregnated plywood using a generalized mathematical description using Bezier curve based on experimental studies. In accordance with the obtained temperature distributions, using Bezier curve, with the help of modeling the charred zone, it was possible to depict in detail the process of charring of samples-fragments of a wooden beam without fire protection and with fire-resistant cladding based on impregnated plywood with a layer thickness of 10 mm and 20 mm. Also, in accordance with the standard temperature regime of the fire, the dependences of the side and end thicknesses, charring rates of the examined fragments-samples of wooden beams depending on the exposure time were determined, and the appearance with the corresponding regression coefficients was determined. The results of exposure of samples-fragments of wooden beams with fireproof lining on the basis of impregnated plywood of different thicknesses and without fireproof lining are also revealed. Sample research was based on visual and graphic analysis of charring depth, which testified to the effectiveness of fire-resistant cladding based on impregnated plywood.

Serhii Pozdieiev, Yana Zmaha, Olga Nekora, Mykola Zmaha, Vadym Nizhnyk
Thermal Degradation Spruce (Picea abies L.) by Thermal Loading

Spruce (Picea abies L.) is one of the most widespread trees for wood processing in Slovakia, with the widest application (production of plywood, laths, fibrous and graded boards, raw materials for the paper and pulp industry, production of musical instruments). As a natural material, it does not resist the influence of initiation sources (flame, radiant heat). The aim of the article is to monitor the influence of the distance of spruce (Picea abies L.) samples from the thermal loading source on the process of its thermal degradation and ignition time. The samples were tested for hob equipment, using the EN 50281-2-1 methodology. The results of the experiment showed an exceptional increase in time and temperature dependence at the same distance of the sample surface of radiant heat. Thermal degradation of the sample touching the surface began to thermally degrade at a hot-plate temperature of 186.6 ℃ in 405 s.

Jana Jadudova, Michal Šudy, Iveta Markova
Physico-Chemical and Thermal Transformations of Wood of Long-Term Natural Ageing

In this paper, the physicochemical and thermal transformations of long-term naturally aged wood are investigated. The results obtained indicate a significant loss of chemical and thermal stability of wood composite as a result of natural aging with hydrolytic destabilisation of the lignocarbohydrate complex, as well as disturbance of the morphological structure of the material. It is shown that lignocarbohydrate materials of long-term natural ageing are characterised by abnormal intensity of the charring process and heat release, as well as increased tendency to smouldering combustion. A new hazard, previously not taken into account in fire resistance standards and assessments, has been discovered – a decrease in the fire resistance of long-life wooden structures. The significant influence of the factor of operation time is caused by the increase in the charring rate of wooden structures. Thus, for a load-bearing wooden beam with a service life of 150 years, the charring rate increases on average by 1.8 times compared to modern softwood structures. It has been experimentally established that changes in physical, chemical and mechanical properties of long-life wood under the influence of high temperatures or fire can lead to a reduction in the fire resistance limit of a wooden structure due to the loss of load-bearing capacity by more than 2 times.

M. M. Almenbaev, J. K. Makishev, B. J. Rakhmetulin, A. B. Sivenkov
An Innovative Engineered Wood Product Made from Densified Wood with Enhanced Fire Performance – State-of-the-Art

As an environmentally friendly wood-modification method, thermo-hydro-mechanical (THM) densification is being developed to improve the intrinsic mechanical properties of wood. However, there is limited investigation on its scale-up application and fire performance of the resulting product. Therefore, the potential of applying THM densified wood in Engineered Wood Products (EWPs) with enhanced fire performance was explored through a review of related studies. The state-of-the-art indicates the importance of material selection and species specific THM process parameters on the scale-up application. Considering the fire safety, the densification itself slightly influences the reaction to fire of wood while its excellent mechanical properties at room and elevated temperature could be able to improve the fire resistance by provide additional residue load-bearing capacity to keep structural integrity in the fire. To further enhance its fire safety properties through delaying ignition time and decreasing the heat-release rate, fire-retardant impregnation and delignification could be combined with densification. Nevertheless, the impregnation and delignification require a complicated and long processing time, high chemical consumption, and the compatibility increases the environmental footprint of the final product.

Lei Han, Ulises Rojas-Alva, Matthew Schwarzkopf, Jaka Gašper Pečnik, Dick Sandberg, Grunde Jomaas, Andreja Kutnar
Effect of Accelerated Aging Weathering on Fire and Mechanical Properties of Plywood

This study is focused on the impact of aging on the fire and mechanical behavior of a fire-retarded industrial plywood claimed for outdoor use as cladding. Two sets of okoume-based (Aucoumea klaineana) plywood, with and without flame retardant, were examined: one aged 4 weeks by immersion in hot water (40 ℃), and the second aged with artificial UV light coupled to spraying for 12 weeks. Scanning electron microscopy coupled with EDX analysis were used to investigate changes in the material after aging, and distribution of flame retardant in the material. This study reveals the impact of different aging procedures on the physico-chemical modifications of the composite material. In addition, the mechanical properties of aged plywood were measured by static bending tests and vibration analysis as non-destructive method to assess weekly the aging effect. Thus, the fire behavior of the sets of plywood as a function of aging exposure time was evaluated by cone calorimetry. The results show that, whatever the aging, it occurs a microstructural degradation of wood and a fast leaching of the flame retardant in whole wood plies, especially for immersion aging. The mechanical properties are then reduced and the fire retardancy is quickly ineffective after aging.

Samia Belhadj, Clément Lacoste, Rodolphe Sonnier, Stéphane Corn
Study of the Atomization Fragmentation Mechanism Under the Electrostatic Field

In the process of liquid electrostatic atomization, the electrodynamic force will play an important role in the development of surface fluctuations, which is the problem of instability of surface fluctuations of liquid jets. This paper analyses the linear stability of non-Newtonian jets (viscoelastic planar liquid film and cylindrical jets) and Newtonian jets (viscous cylindrical jets) with small surface perturbations in the radial electric field, deduces the dispersion equations, and accordingly discusses the influence of dimensionless parameters such as the electric Euler number, the Weber number, and the Reynolds number on the stability of these jets. The atomization mechanism of the viscous cylindrical jet is initially studied by analyzing the linear stability of the viscous jet in the radial electric field, which provides a certain theoretical basis for the extinguishing of the charged fine water mist.

Yuzhen Wu, Xin Liu, Zhenyu Xu
Chemisorption Trends of Oxygen on Freshly Pyrolyzed Wood Charcoal

The ignition of wood is a multistage process, with the first major thermo-chemical conversion step being the pyrolytic disintegration of the material, forming a highly reactive intermediate, charcoal. Dependent on the pyrolysis temperature and duration, charcoal can exhibit different properties. In this study, preliminary results from a recently started project, concerned with the impact of the pyrolysis temperature and duration on the reactivity and the propensity for chemisorption of oxygen on freshly formed charcoal, are reported.Milled beech and spruce wood are examined in a Simultaneous Thermal Analyzer (STA) by first being pyrolyzed at six consecutive heat treatment temperatures (HTT), 350 ℃ to 600 ℃, with 50 ℃ increments under nitrogen flow. After cooling to room temperature, a combustion step is performed in air to a maximum temperature of 600 ℃. During this heating step an increase in the mass (TG signal) of the charcoal samples can be seen and at same time the DSC signal already exhibits exothermal events. These exothermal events are considered to be the result of oxygen being chemisorbed on the porous charcoal structure with a high internal surface and one of the reasons for self-ignition of charcoal.By producing wood char at specific HTT followed by a combustion step, the propensity of the charcoal of two of the most used European wood species towards chemisorption of oxygen and heterogeneous combustion are methodically analyzed at a microscale.

Christoph Preimesberger, Christoph Pfeifer, Christian Hansmann
Preparation of Glass Sampling Containers to Determine Trace Amounts of Accelerants in Fire Samples

Gas chromatography is be used to prove the presence of small amounts of organics trapped on solid samples or in liquid samples from fires and it serves as evidence of the presence of traces of flammable liquids used as substances that support combustion (fire accelerants). Demonstrating the presence of traces of gasoline or diesel fuel can significantly support the hypothesis that a fire was started intentionally. Recently, with the development of gas chromatography instrumentation, the sensitivity of the measurement increases and it is possible to measure lower concentrations. Therefore, it is important to collect the sample correctly, use clean sample containers, collection tools and equipment and prevent contamination of the sample during transport to the laboratory. This places increased demands on the quality of the collected samples and their packaging – sample containers. The contribution deals with the testing of the cleanness of glass sample containers and suggests their cleaning procedures so that their contaminants do not affect the determination of the presence of traces of gasoline or diesel in samples from the fire scene. Gas chromatography with mass spectrometry and solid phase micro extraction (GCMS-SPME) was used to detect contamination in new preserving jar with TWIST OFF caps. By testing different types of lids from different manufacturers it was found that all of them are already contaminated with similar substances to varying degrees. Various methods of cleaning were tried, namely burning, using sorbent materials and cleaning with solvents. Based on these results, a procedure for their cleaning was proposed.

Petra Bursíková, Milan Růžička, Ondřej Suchý
Report from Case Studies: Fire Chemistry and Fire Visualisation in the Classroom

In the Estonian Academy of Security Sciences higher education curriculum “Fire Chemistry and Physics” module learning outcomes state that students should be able to describe indoor fire dynamics phases and carry out simple thermal engineering fire safety and combustion chemistry calculation tasks. The aim of the study is to make suggestions to lecturers of fire chemistry on how to support students’ learning in the area of wood ignition and burn with the help of simulations. We analysed case studies conducted by students individually (n = 34) as well as in groups (n = 9). Out of the materials chosen for fire chemistry calculation tasks in our sample, wood is the most used material because it exists in almost each room selected by students. The study combines theoretical analysis with practical educational approaches to provide an overview of the importance of wood in fire chemistry and physics. It gives insights into what tasks have helped the students’ comprehension of wood combustion processes. The results indicate that there are rare cases (e.g. sauna fires) when the kindling material is wood. However, students have selected substances in wood composition like cellulose, lignin and hemicellulose for oxygen consumption calculations. Our results indicate that providing significant tasks where the students are autonomous in choosing the target case and simulation software, deep learning is supported. We suggest that a new visualisation and modelling software should be developed to improve students’ knowledge and skills about fire chemistry and physics.

Reet Kasepalu, Stella Polikarpus, Kärt Reitel, Regina Kaasik

Wood Burning Retardation and Wood-Based Materials

Development of Boron Based Additive for Medium Density Fibreboards with Improved Flame Retardancy

Medium density fibreboards (MDF)s are one of the most common wood based panels with aesthetical and functional advantages. They have very versatile usage areas such as furniture, cabinets, shelves, floorings, doors and door frames. However, wood fibres are not resistant to flame that limits application areas. To overcome this problem, a novel flame retardant additive was synthesized that based on boric acid. Medium density fibreboards were pressed with the addition of developed chemical at laboratory scale and compared with non-treated sample. Flame retardant MDFs were successfully pressed without compromising of any mechanical properties such as internal bond and bending strength. Only, the swelling behavior should be developed with water repellency agents like paraffin. In addition, this flame retardant helps to reduce formaldehyde content and acts as formaldehyde scavenger. Thermal properties of medium density fibreboards have been determined by means of differential scanning calorimetry (DSC) and Thermogravimetric Analysis (TGA). Furthermore, the attitude of combustion was investigated by cone calorimetry method to determine the fire behaviour. According to results, the developed additive has a potential for flame retardancy in wood based panel industry.

Ümran Burcu Alkan, Başak Bengü
Charring Behaviour of Cross Laminated Timber (CLT) Members: Effects of Fire Retardant Treatment

Engineers and architects worldwide express an ever-increasing interest in using CLT in construction, which is hindered by the combustible nature of timber. An effective way of addressing this issue is by treating the CLT element with a Fire Retardant (FR). In this work, the charring rate of non-treated and FR-treated CLT specimens is compared. The experimental investigation employed 150 mm × 100 mm × 65 mm spruce CLT specimens that were exposed, in a vertical position, to a constant 75 kW/m2 radiative heat flux, using a porous burner. Based on the temperature profiles, the mass loss, the heat release rate and the charring rate measurements, the improvement of the FR-treatment on the overall fire behavior of the CLT elements was quantified. In addition, four different charring rate correlations were validated against the obtained experimental data, aiming to determine their relevant prediction accuracy.

Andrianos Koklas, Iasonas Filippidis, Dionysios I. Kolaitis
Thermal Properties of Borax/Lauric Acid-Impregnated Wood

Phase change materials (PCMs) are solid materials that absorb and release large amounts of latent heat during a phase change. However, the biggest disadvantage of phase change materials is that they are flammable. In this study, we used borax (BX) to develop a non-flammable PCM to examine the properties of beech wood samples. For this purpose, an oil/water emulsion was prepared by adding 10% lauric acid (LA) to the BX aqueous solution prepared at 5% concentration. Beech wood samples were impregnated with the prepared mixture using vacuum/autoclave. TGA (thermogravimetric analyzer) and DSC (differential scanning calorimeter) analysis and MFT (Mini Fire Tube) method, which is an adopted and a modified ASTM E69 method, were used to thermal properties including phase change temperature, enthalpy, thermal stability. According to Mini Fire Tube (MFT) test results, 78% weight loss and maximum temperature 392,2 $$^\circ {\text{C}}$$ ∘ C was observed in the control samples, while 34% weight loss with max. Temperature 221,3 $$^\circ {\text{C}}$$ ∘ C were observed in 5% BX + 10%LA treatment in 300 s. The results show that impregnated wood phase change enthalpy of 42.2 J/g, and phase change temperature of 55.29 $$^\circ {\text{C}}$$ ∘ C .

Ahmet Can, Wojciech Grzeskowiak
The Progressive Test Method for Assessing the Thermal Resistance of Spruce Wood Treated with Flame Retardants

The article is focused on evaluating untreated and flame retardant treated spruce wood (Picea abies (L.) H. Karst), used as a building material, using a new laboratory test method according to utility model no. 9589. This work aimed to evaluate the effect of different flame retardants applied to spruce wood, in terms of thermal resistance after being loaded with a flame source, depending on the angle of inclination of the sample. The wood samples were treated with three different retardation treatments: expandable graphite was used in combination with water glass, Bochemit Antiflash and Bochemit Pyro. Using this method, we can evaluate the spread of the flame, the mass loss, and the burning rate. During the experiment, we measured the temperature on the surface of the samples using a thermal camera. The results of applying the laboratory test method showed a significant effect of the angle of inclination (0°, 45°, 90°) of the sample and the use of flame retardants on the evaluation criteria. The best results among all flame retardants were achieved by expandable graphite in combination with water glass, in all evaluation criteria.

Elena Kmet’ová, Danica Kačíková, František Kačík
Exploring the Influence of Thin Intumescent Coatings on the Onset and Rate of Charring for Mass Timber During Fire

This experimental fire study investigates the application of two thin intumescent coatings on mass timber (CLT), to assess their capacity as a means of passive fire protection to delay the onset of charring and reduce the charring rate of timber. Coated and exposed timber samples were subjected to a heat flux of 50 kW/m2 for 60 min. The bare timber samples experienced rapid ignition and flaming upon exposure to heat, resulting in char fall-off during testing, while the surface of the coated timber samples intumesced rapidly, developing a thick, insulating layer. In addition, sporadic cracking was noted on the surface of the intumesced coating – generally along the edges of the samples and between timber boards – caused by separation of the timber surface underneath due to charring and regression. Where cracking was more pronounced for the coated timber samples, localised flaming was witnessed of the timber underneath. The experimental findings demonstrated that thin intumescent coatings can effectively delay, but not completely prevent, the onset of timber charring (assumed in this study to occur when timber reaches 300 °C). Outcomes of this study also showed that the rate of charring was reduced to about half for timber coated with thin intumescent coatings. It is worth mentioning that the change in the (1) onset of charring and (2) rate of charring is specific to the timber samples and test conditions chosen for these experiments; more specifically, the thickness of the applied coating and severity of the heating condition (i.e., incident radiant heat flux).

Stavros Spyridakis, Cristian Maluk
Classification Tests of the Reaction to Fire of Modified Cellulosic Materials Encrusted with Expandable Graphite

Despite a large amount of data on innovative fire protection technologies for wood and lignocellulosic materials, the primary trend is creating fire retardant preparations using compounds based on phosphorus and/or boron. Additives that promote the formation of a char layer during the combustion of lignocellulosic materials are effective flame retardants. Expandable graphite [EG] is undoubtedly one of the intumescent agents group’s more environmentally friendly flame retardants. The work aims to develop cellulose-based composite board materials with class B potential according to the EN 13,501–1 standard [1]. The materials manufacturing process includes the following stages: mixing additives and cellulose fibers, fiber flotation, water removal, and drying the final product. The materials were analyzed for fire properties in accordance with ISO 5660–1 [2], EN 13,823 [3] (the so-called SBI test), and EN ISO 11925–2 [4] (flammability from a small flame). As a result of the research, the influence of the presence of EG and boron compounds on the reaction to fire of the produced insulating board materials was demonstrated.

Bartłomiej Mazela, Wojciech Grześkowiak, Waldemar Perdoch
Improving the Fire Performance of Chemically Modified Pine (P. Sylvestris) Sapwood by an Integrated Modification Approach

Natural wood has been widely used for construction and building purposes. However, wood is susceptible to wood-destroying organisms moisture-induced dimensional changes and fire. Although chemical wood modification technologies with thermosetting resins like phenol-formaldehyde (PF) may compensate durability and swelling issues, the latter may not enhance fire resistance. To address this issue, Scots pine sapwood (Pinus sylvestris L.) has been impregnated with a formulation of a PF resin and a phosphate-nitrogen-based flame retardant. The reaction to fire of the treated material was assessed through thermogravimetry analysis, Bunsen burner test (Pries and Mai), small burner box (ISO 11925–2) and cone calorimeter measurements (ISO 5660–1). Results indicated that pure PF resin treatment slightly improved thermal stability and reduced flame spread. However, it led to a significant increase in heat release peak and smoke production. In contrast, incorporating the flame retardant with PF resin demonstrated notable improvements in fire resistance independent of the test method applied. Compared to pure PF-treated wood, thermogravimetry analysis revealed a 31% increase in final char residue. The Bunsen burner test exhibited great self-extinguishing properties and the small burner box test demonstrated a 56% reduction in flame height. Cone calorimeter tests confirmed a substantially inhibited heat release with no ignition during the test. Notably, the total smoke production was also significantly reduced, even lower than the untreated wood. These findings emphasize the effectiveness of the combined PF resin and phosphate-nitrogen-based flame retardant treatment in enhancing the fire resistance of wood.

Muting Wu, Lukas Emmerich, Holger Militz
Fire Protection of Wood Using a Coating Based on Sodium Silicate and Biochar

Wood is one of the most frequently used building materials. However, due to its composition, it is flammable, which causes complications when using it. Coatings are one of the options for protecting wooden structures from the effects of fire. The article deals with the possibility of producing such a coating by combining water glass and fine biochar particles. Both components of the coating were combined in several proportions and then applied to the surface of the spruce wood. The samples treated in this way were finally measured using a cone calorimeter.

Peter Rantuch, Veronika Kvorková, Jozef Martinka, Tomáš Štefko, Igor Wachter

Fire Modeling, Testing, Certification

Enhancement of Fire Test Stand Performance at Test Site of BAM: Installation and Evaluation of an Augmented System with a Fire Reference Package

Packages for the transport of radioactive material are designed to endure severe accidents. Packages for the transportation of radioactive material must demonstrate that the package can withstand certain prescribed tests from the IAEA Regulations [1]. In addition to mechanical tests, a thermal test in form of a fire test must be carried out. As packages to be tested at BAM are significantly larger than previous package designs, BAM has expanded an existing fire test stand. A modular concept is chosen, which means that the arrangement of the burner nozzles can be adapted to the test specimen. The dimensions of the burner rings, the type, the orientation and the number of burner nozzles can be varied depending on the test specimen. In addition, various pumps can be used to set the corresponding mass flow. With the help of a calorimeter test, the fire test stand can be qualified for a specific size of packages regarding the boundary conditions of the IAEA Regulations [1]. Due to the typically wood filled impact limiters in German package designs, a fire test is necessary, as experiments have shown that possible openings that occurred during a mechanical test contributed to the ignition of the wood filled impact limiters within the prescribed 30 min of the IAEA Regulations [1]. From a series of experiments, two experiments are presented to show the possibilities to obtain different temperatures and temperature rates in the test specimen. In addition to sensor data, the heat flux into the package is calculated to verify that the IAEA boundary conditions are satisfied. In addition to the temperature data, other data such as wind speed and wind direction are also recorded to explain subsequent effects in the measurement data in a comprehensible manner.

Tobias Gleim, Martin Feldkamp, Thomas Quercetti, André Musolff, Jan Werner, Frank Wille
Room-Corner Tests with Exposed Timber

Fire experiments were conducted to observe the effect of varying amounts of exposed timber wall and ceiling assemblies in a standard room-corner fire test. The standard test, NFPA 286 (Fire Tests for Evaluating Contribution of Wall and Ceiling Interior Finish to Room Fire Growth) is based on a room with a door opening at the front and a gas burner located against a back corner. Pass or fail criteria for flashover are provided for the test, with the test lasting up to a maximum of 15 min. Three experiments were conducted that comply with the 2021 International Building Code for amount of exposed mass timber. For each experiment, the propane burner profile was identical. Instrumentation used during the experiments included thermocouples, a heat flux transducer, and a heat release rate exhaust hood. Based on the time to flashover criteria in the standard, flashover was not observed in any of these three tests.

Laura E. Hasburgh, David Barber, Keith J. Bourne
Fire Experimental Testing of STS-Reinforced Glulam Beam-End Connections with Metal Connectors’ Wood Protection

This paper presents the results of an experimental study on the fire performance of minimally fire-protected wood-steel-wood (WSW) beam connections strengthened with self-tapping screws (STS). Two full-size fire endurance tests were conducted on glulam beam-end connections subjected to shear and bending moment. Two connection configurations were investigated, each utilizing four structural steel bolts arranged in two different patterns. The beam-end connections were reinforced perpendicular to the wood grain using six STS and exposed to elevated temperatures that followed the CAN/ULC S101-19 standard fire time-temperature curve while subjected to a load ratio equivalent to 60% of the maximum design moment of the weakest unreinforced connection configuration. The test results show that the failure time of both connection configurations conveniently exceeded 50 min, which surpassed the 45-min minimum fire resistance rating required by applicable building codes. The connection with the first bolt pattern, in which two rows of bolts were symmetrically positioned near the top and bottom sides of the beam section, performed better than that with the second pattern, in which the bottom row of bolts was raised to the mid-height of the beam section, and had a failure time surpassing 60 min under standard fire exposure. Most importantly, reinforcing the connections with STS prevented splitting or row shear failures, which are frequently encountered in unreinforced WSW connections.

Oluwamuyiwa Okunrounmu, Osama Salem, George Hadjisophocleous
Combustion Chamber Design for Encapsulated Wood-Component Testing

Heavy-weight packages for the safe transport of radioactive material are equipped with impact limiters often built of wood-filled steel sheet structures to fulfil the requirements of the International Atomic Energy Agency (IAEA) regulations. The requirements define mechanical tests followed by a thermal test, including criteria ensuring the package design’s ability to withstand severe accidents and provide a high level of technical safety.Impact limiters are a package component mainly designed for the packages to withstand severe mechanical accident scenarios. In drop tests the impact limiters absorb the kinetic energy during impact of the package. The package must then - with its pre-damaged impact limiters - endure a thermal test defined precisely in the IAEA regulations as a 30-min fully engulfing 800 ℃-fire. After the fire, a wood-filled impact limiter may continue to release thermal energy from an ongoing combustion process, defining relevant package temperatures. The energy flow from a possible burning impact limiter to the package is important for the safety evaluation of transport packages. To investigate the combustion behaviour of densely packed layers of spruce wood, encapsulated in pre-damaged cylindrical metal enclosures, a test set-up has been realised. The set-up consists of a combustion chamber to perform these tests under defined boundary conditions. The temperature development of the test specimens will be observed from outside with a thermographic imager, with HD-Cameras, and the mass loss will be measured during the entire test. Airflow conditions in the combustion chamber are analysed using Computational Fluid Dynamics (CFD) calculations in OpenFOAM. The planned combustion test setup is described.

Martin Feldkamp, Tobias Gleim, Thomas Quercetti, Frank Wille

Smoke Control and Combustion, Toxicity, Dust

Scale Law Study of the Combustion Toxicity of Acrylonitrile-Butadiene-Styrene

The toxic gases released during polymer combustion are the primary lethal factors in fires. This paper focuses on investigating the scale law of polymer combustion toxicity using acrylonitrile-butadiene-styrene (ABS) as a sample. The concentration of toxic gases released from small-scale combustion of ABS materials was measured under different ventilation conditions using a steady-state tube furnace. Additionally, numerical simulations were conducted using FDS software. The simulation results demonstrated a good agreement with experimental data, confirming the validity of the Computational Fluid Dynamics (CFD) model. Building on this foundation, the Froude number was maintained constant, and multi-scale CFD models were established. The results revealed that as the experimental scale increased, the concentration of CO around the fuel also increased. Moreover, when the ventilation conditions transitioned from good to poor, the growth rate of CO concentration increased proportionally with the growing experimental scale. These two parameters exhibited a linear function relationship.

Zong Ruowen, Bai Jingwen, Wang Jiyun
Study of Resistivity of Beech Wood Dust Depending on Particle Size

Different types of combustible dusts are used in industry. These dusts can cause an explosion. The wood industry works almost exclusively with combustible dusts. Assessment and evaluation of fire engineering dust parameters is a complex problem. One of the parameters is the dust resistivity according to the EN ISO/IEC 80079:20-2 standard. Dust resistivity according to this standard is the specific conductivity of the dust sample. Based on it, it is possible to determine the resistivity of conductive (Group IIIC) or non-conductive (Group IIIB) dust according to the standard. In the case of non-conductive dusts, it is possible to predict the danger of dust in industry (generation of static electricity) based on the size of the specific conductivity. The article deals with the conductivity of beech wood dust and is aimed at assessing the conductivity of this wood depending on the particle size from 0 µm to 180 µm.

Richard Kuracina, Zuzana Szabová, László Kosár
Study of Minimum Ignition Temperature of Beech Wood Dust Clouds Using Different Types of Dispersers

Combustible dust in the form of a layer or dust cloud occurs very often in industry, and under certain conditions this dust can ignite from a hot surface. This combustible dust is also often found in the woodworking industry. The minimum ignition temperature (MIT) of a dust cloud from a hot surface is determined in accordance with EN ISO/IEC 80079-20-2:2016 Explosive atmospheres Material characteristics. Combustible dust test methods. According to this standard, the device for determining the MIT of dust cloud does not have precisely defined design parameters. This paper deals with the measurement of the MIT of a dust cloud from a hot surface on a device with two design solutions - an older disperser type and a new cone type. The minimum ignition temperatures of wood dust samples using both dispersers are compared.

László Kosár, Richard Kuracina, Zuzana Szabová
Smoke Emission from Wood and Wood Based Products

This paper deals with the smoke emission from wood and wood-based products. The amount of smoke released from organic polymers (e.g. wood and wood-based materials) is commonly quantified by smoke extinction area per mass loss of sample. The impact of sample density, external heat flux exposing sample surface, trees kind (coniferous and deciduous) and extractives content in samples for oak wood, spruce wood, and pinewood on the smoke extinction area per sample mass loss was investigated in this study. The cone calorimeter test (at three different external heat fluxes: 25, 35, and 50 kW/m2) measures the extinction area of smoke released from the investigated wood. The obtained results proved the significant impact of wood species (extractives content) on the smoke extinction area. The average smoke extinction area per sample mass loss for all investigated wood species lay in the interval from 4.6 to 81.5 m2/kg (standard deviation was up to 20.5 m2/kg). However, the pinewood (the sample with the highest content of extractives) shows a significantly higher smoke extinction area per sample mass loss (61.8 to 81.5 m2/kg) than oak wood (4.6 to 18.2 m2/kg) and spruce wood (10.7 to 29.5 m2/kg). Besides that, both the external heat flux (exposing sample surface) and sample density have no negligible impact on the smoke extinction area per sample mass loss.

Jozef Martinka, Peter Rantuch, Igor Wachter, Tomáš Štefko
Explosion Parameters of Cellulose Based Materials

The main component of wood is cellulose. Cellulose is a plant polysaccharide that forms wood with other substances (lignin, hemicellulose). Wood can be considered a combustible substance and each of its components is flammable. Cellulose has multiple uses, e.g. as paper, in the form of derivatives as a filler in pharmaceuticals or in the food industry. In industry, it is therefore necessary to know their fire parameters, especially regarding the possibility of explosion or fire. Dispersed cellulose and its derivatives have various explosion parameters. This article deals with the study and comparison of explosion parameters of different types (microcrystalline) and cellulose derivatives (Hypromellose) samples. The lower explosive limit of microcrystalline cellulose (MCC) was 500 g.m−3 and Hypromellose (HPMC) 125 g.m−3. The maximum explosion pressure of the samples was 5,624 bar (MCC) and 7,441 bar (HPMC). The explosion constant, Kst, of the samples was 26,65 bar.m.s−1 (MCC) and 122,19 bar.m.s−1 (HPMC). Therefore, when cellulose based materials are used, stored, handled or transported, it is necessary to know their explosion parameters to design effective explosion prevention measures.

Zuzana Szabová, Richard Kuracina, László Kosár

Fire Safety in Wooden Objects

Application of Iterative Fire Severity Analysis to Fire Safety Design of Multi-storey Mass Timber Structures

The United Nation’s sustainable development goals to mitigate climate change and the New Zealand Government’s Climate Change Response (Zero Carbon) Amendment Act 2019 have encouraged the construction industry to utilize timber as a primary construction material. When exposed to fire, timber burns and forms an insulative char layer that provides protection to the unburnt load-bearing timber. Encapsulation can be provided to delay the start of charring. After flashover, exposed mass timber surfaces will burn and contribute additional fuel load. This paper illustrates the use of an iterative fire severity analysis based on a parametric compartment fire model to account for the contribution of non-encapsulated timber during post-flashover fires. A 5-storey, cross laminated timber residential building with sprinkler protection is used as a case study to investigate reasonable fire resistance ratings for design. Sensitivity analyses of fire resistance ratings show a linear relationship with fire load from 250–800 MJ/m2, and an exponential relationship with ventilation resulting from 19% to 64% of window breakage. For the post-flashover fire scenarios considered, the fire resistance rating ranges from 30–60 min subject to the design assumptions and inputs adopted.

Dennis Pau, Andrew Buchanan, Cameron Douglas
Thermal Finite Element Analysis of a Post-Tensioned Timber Connection

Post-Tensioned Timber (PTT) structural systems have many advantages over conventional timber frames including low-damage, re-centring and fast construction. To design these connections for fire the 3D thermal field of the connection is needed. This paper compares 3D thermal finite element analyses and a previously tested large scale PTT beam-column sub-assembly loaded and exposed to the Standard Fire. The modelled temperatures for the interface and shallow depths in the timber were similar to the experimental results, but temperatures deeper in the timber were cooler. The results show that the thermal and mechanical response of PTT beam-column connections are interdependent and both must be considered together when designing these connections.

Paul Horne, Anthony Abu
Load-Bearing Timber-Framed Gypsum Plasterboard Walls Subjected to Two-Sided Fire Exposure

Gypsum plasterboard lined timber-framed walls are commonly used in construction and provide excellent fire-resistance. When these walls are required to perform a load-bearing function, fire-resistance is generally assessed by standard fire-resistance testing, exposing a specimen to fire from one side only. When load-bearing walls are themselves not fire separations, they can potentially be exposed to fire from both sides simultaneously. No current tests exist to reliably measure the performance of such gypsum plasterboard lined walls and there is very limited information for a recognized fire engineering design method. In this research, Abaqus/CAE finite element software was used to develop thermal and structural models for such walls subjected to one and two-sided fire exposures which were validated using the experimental results. The experimental and modelling results were then analyzed to formulate a predictive design method enabling designers to assess the structural adequacy of such walls subjected to two-sided fire exposure.

Hohyung Kang, Anthony Abu, Peter Moss, Hans Gerlich, Richard Hunt
Wood-Wood System Connection for Elements - A Hook-in System. A Fire Protection Case Study of a Multi-storey Timber Building

In timber construction, many wood-wood connections have bar-shaped components. As yet, for cross-laminated timber (CLT), wood-wood connections are still not available. The Department of Timber Construction at the University of Innsbruck has therefore developed the “double dovetail tenon”, a system connector made of laminated veneer lumber (LVL) made of spruce. It consists of two dovetail-shaped tenons that are rotated 180° at their overlapping surface. With this system connector, the orientation of the veneers and the inclination of the flank surfaces can be varied. The fire tests are carried out analytically, based on existing research from the literature and fire tests already investigated on metal and wood joints of similar size and joint shape. The fire protection investigation is carried out in two steps: Observation of the components of the system connection (connectors, CLT) as well as the combination when installed. A significant difference to conventional wall-ceiling-wall connections is that the ceiling is vertically inserted into the wall element. The system connector is fully integrated into the components to be connected. Due to assembly tolerances and wood shrinkage/swelling, a gap must be allowed for. Precision deviations due to the CNC joinery must also be taken into account. These and other considerations are investigated using the example of a multi-storey timber building with different installation options for the system connection. In contrast to metal system connectors, the wood connector does not heat the entire connector, but only the parts of the connector directly exposed to the flames.

Anton Kraler, Martin Saltuari, Andreas Pomaroli
Fire Safety Solutions in Finnish Multi-story Timber-Frame Buildings

Since the early 1990s, Finland has been actively engaged in the development of multi-story timber-frame buildings in collaboration with other EU countries. Following a brief trial period for constructing wooden apartments (1995–1997), amendments were made to Finnish fire code in 1997, allowing the utilization of timber in the structural frames and exteriors of buildings up to 4-story. In 2011, further revisions to the fire code enabled the construction of wooden buildings ranging from 5–8-story in height. According to the size specifications outlined in the current Finnish fire regulations as of January 1, 2018 (Ministry of Environment Decree 848/2017), it is feasible to erect residential, office, hotel, and care center with timber frames and facades, extending up to 8-story. Additionally, buildings exceeding 8-story can be achieved with the implementation of a functional fire safety inspection. In Finland, wooden buildings exceeding 2-story must be equipped with an automatic sprinkler system. The load-bearing wooden framework should primarily be safeguarded with A2-s1,d0 class fireproof protective coatings, typically consisting of gypsum boards. Furthermore, thermal insulation must meet at least an A2-s1,d0 fire class rating, typically achieved with mineral wool. Fire barriers should be integrated into the ventilation gap and eaves of wooden facades. While facades may have a wooden appearance (fire class D-s2, d2), it is mandatory for the facade of the ground floor to be constructed using a fire class B-s2,d0 material. As of January 2024, Finland has completed the construction of 175 wooden apartments buildings exceeding 2-story, totaling 5,742 apartments.

Markku Karjalainen, Hüseyin Emre Ilgın
Structural Integrity Assessment of Two-Story Cross-Laminated Timber House Under Fire Load

Fire generates considerable thermal load on building, challenging the sturdiness of load-bearing timber elements. The mechanical characteristics of wood, such as strength and stiffness, undergo significant changes under the influence of heat. As temperature increases, wood degrades in both its superficial integrity and structural properties, compromising the load-bearing capacity of the entire structure. This requires a comprehensive understanding of the effects of fire on timber, embracing both the immediate consequences of direct exposure and the potential residual impact on structural performance. This paper investigates the structural integrity of a two-story house constructed with cross-laminated timber (CLT) panels subjected to simulated fire load. The theoretical framework covers an exploration of fire loads on buildings, the influence of fire on the mechanical properties of wood, and existing standards describing the structural integrity of wood elements under fire conditions. Through a comprehensive analysis, the research aims to clarify the performance of CLT structure during fire event, providing valuable insights for structural engineering. The findings presented herein contribute to the evolving understanding of timber construction resilience in the face of fire hazards, forming future design considerations and enhancing the overall safety of wooden structures in urban environments.

Róbert Uhrín, Michal Gregor, Patrik Štompf, Jozef Štefko
Fire Safe Use of Wood in Buildings - Global Design Guide

Building codes around the globe dictate the design and construction of buildings. For most buildings, designers will follow prescriptive code provisions to demonstrate code compliance. However, some building codes allow the use of performance-based design allowing for greater flexibility in the selection of materials and systems. Regardless of the code compliance methods, the combustibility of timber structures and wood products needs to be well-understood and properly accounted for in the building designs. This paper describes the development of a new international design guide within the Fire Safe Use of Wood (FSUW) network, written by 13 lead authors assisted by more than 20 experts in over a dozen different countries.

Alar Just, Andy Buchanan, Birgit Östman, Michael Klippel, David Barber, Ed Claridge, Christian Dagenais, Andrew Dunn, Paul England, Marc Janssens, Esko Mikkola, Colleen Wade, Norman Werther
Fire Safety Design of Structures in Steel-Timber Hybrid Construction

In the structural design of steel-timber hybrid constructions, linear steel load-bearing elements such as columns and beams protected by timber linings, as well as frame systems, which are completed by a secondary load-bearing structure consisting of plane CLT elements can be used. However, for associated multi-storey buildings, there are also high fire protection requirements that must be met to ensure the overall safety of the building. A consistent and widespread implementation of this construction method in building practice is, therefore, currently failing due to corresponding knowledge gaps. The findings and results on the fire behaviour of steel-timber hybrid structures from the first tests series obtained to date as part of the ongoing research project will be presented in the following paper. A campaign with three different experimental test setups was conducted. Small scale specimens were used to derive and validate thermal properties for numerical simulations. Furthermore, the protective effect of timber linings for steel members was investigated in beams, columns and floor systems. The tests have shown that the charring behaviour of the timber linings and therefore the failure time depend on numerous factors like the number of sides exposed to fire, the profile factor of the protected steel member as well as of the joints in the applied linings.

Patrick Dumler, Jakob Blankenhagen, Norman Werther, Martin Mensinger, Stefan Winter
The Outlook for Wooden Buildings in the Czech Republic from the Point of View of Technical Standardization Committee 27 Fire Safety of Buildings

There is currently a sufficient amount of wood in the territory of the Czech Republic, enabling its wide use in several areas. One of these is the construction industry. The idea of more extensive use of wood is also closely connected with the circular economy and thus with environmental protection. However, there are also certain restrictions relating to the construction of wooden buildings, e.g. from the point of view of fire safety. These restrictive requirements are related to the material and structural design of wooden buildings. As can be seen from research, the restrictive requirements for wooden buildings in the Czech Republic are generally comparable those in other countries. Research is currently being carried out in the Czech Republic addressing the possible modification of these restrictive requirements. The goal should be the wider use of wood in buildings even with the application of design standards addressing fire safety. Nevertheless, the continued application of the fire safety engineering procedures widely used in this area can still be assumed.

Jiri Pokorny, Alexandra Kardosova, Lenka Brumarova
Temperature Measurements in Timber Exposed to Fire Using Thermocouples

Fire tests on non-loaded steel-timber composite elements and their numerical simulation are achieved. Differences between measured and simulated temperatures in timber can be significant, reaching several hundred kelvins. This observation leads us to examine various instrumentation techniques. Inconsistent temperatures are measured depending on whether the thermocouple is parallel or perpendicular to the heat flow, and whether it passes through the fire or in an environment that remains cold. The local thermal disturbance caused by the presence of thermocouples is simulated by the finite element method. This approach allows us to assert that the differences observed between the measured temperatures are due to the contrast between the thermal properties of the used sensors and those of the surrounding timber. The simulation of the thermal field in a timber sample without thermocouple constitutes a comparative basis. It allows us to make evident that thermocouples inserted parallel to isotherms are the only ones able to perform correct temperature measurements in timber. This observation is confirmed by the comparison of charring rates deduced from measured and simulated temperatures with typical combustion behavior of softwood in standard fire tests (ISO 834 heating curve).

Antoine Béreyziat, Maxime Audebert, Sebastien Durif, Abdelhamid Bouchair
The Role of Insurance in Scaling Mass Timber Construction: Review on Enablers and Shortcomings

Forests play an essential part in nature conservation and restoration, biodiversity, climate change mitigation and especially the transformation to a low-carbon economy. However, practices to manage forest environments and scale the sustainable use of innovative timber products (nature-based solutions (NBS)) in place of grey infrastructure construction materials are proving problematic, mainly due to the real and perceived risks of buildings constructed with mass timber or engineered wood. Insurers can play an enabling role in scaling wood construction practices. Yet currently, insurance - with a few essential exceptions - fails to cover mass timber constructions in a way that make them competitive with traditional grey construction materials. This is mainly attributed to a lack of performance data and perceived fire and water damage risks. We review experience of insurers as they enter the wood and timber sector, focusing on mass timber and standards and guidelines to de-risk the sector. We highlight innovative insurance products and their shortcomings and benefits. We find that while interest in insurance for nature conservation and green infrastructure is increasing, gaps in the role of insurance to enable NBS, like mass timber construction, persist.

Irshaid Jenan, Linnerooth-Bayer Joanne, Foreman Timothy, Martin Juliette

Fire in Historical Buildings

Wooden Historical Buildings and Determinants of their Fire Protection as a Challenge for Fire Service Officials and Preservationists

Cultural monuments in the Slovak Republic currently represent a group of objects that are difficult to protect against fire, mainly due to the lack of fire protection measures. A special position in this group is not only all-wood buildings, which are dominated by wooden churches and other sacral buildings, but also partial wooden constructions, such as ceilings, roof trusses, or using shingles as roof coverings on ​​buildings built with fireproof building materials. The article captures the current situation of ensuring protection against fires of such historical buildings from the overall overview of the determinants that have an impact on the occurrence of fire, its spread to the wooden building, or to the wooden building elements of neighboring historic buildings. At the same time, it presents the possibilities of protection against fires using fire engineering equipment, reducing the development of fire until fire intervention by fire brigades. The article further points out the limitations of an effective fire attack against a developed fire caused by the current use of the object and/or the nature of the space adjacent to the originally protected object. It also suggests procedures to solve the fire protection problem of historical buildings in the current legislative situation.

Dušan Hancko, Jaroslava Štefková, Jozef Vadovič
Comparative Analysis of the Flammability Characteristics of Historic Oak Wood from 1869 and Contemporary Wood

The tests are aimed at demonstrating the flammability of historic (old) oak wood compared to the fire resistance of modern oak wood. The tested wood has a similar density and a similar degree of grain. The tests aim to show whether historic wood behaves significantly differently than modern wood during a fire. The dried weighed, and sized samples were subjected to a fire resistance test in an MLC calorimeter using a thermal radiation flux of 35 kW/m2 and 50 kW/m2. Six samples of modern wood and twelve historic wood with similar density and degree of surface damage were selected for testing. Analyzing the results of most flammability parameters, it was shown that old wood, regardless of the surface condition and heat intensity, is characterized by lower values of heat release rate (HRR), total heat released (THR), effective heat of combustion (HOC) and mass loss (ML).). The average ignition time of historic wood at an intensity of 35 kW/m2 is faster than that of new wood by 28.5%, and at 50 kW/m2 even by 54%. However, such a fast ignition time does not negatively affect the weight loss of historic wood compared to modern wood, as it is caused by extensive surface damage. The times for samples to ignite and extinguish in the case of historic wood are shorter than for modern wood. These values, however, do not negatively affect the remaining flammability parameters of the analyzed wood.

Andrzej Jurecki, Marek Wieruszewski, Wojciech Grześkowiak
Research on the Fire Performance of Aged and Modern Wood

The damage caused by fire outbreaks in ancient or old wooden buildings in recent years has been a global concern. To ascertain the reaction of old wood to fire, the thermal, heat release and combustion properties of wood from such buildings must be studied. Hence in this research, microscale combustion calorimetry, thermogravimetric analysis, and cone calorimetry experiments were adopted to investigate the fire properties of 200–300-year-old cypress, pine, and fir along with new wood to comprehend the reaction to fire. It was seen in the research that the fire properties are strongly dependent on the density and structure of the fibres in the wood. Hence, a loose structure formed as a result of weathering and aging burns faster has low ignition times, and produces more heat. An analysis of samples from different parts of the trunk also showed that the sapwood wood exhibits higher fire performance compared to heartwood and samples from the pith/medullary heart.

Cong Jing, Juliana Sally Renner, Qiang Xu

Forest Fires

Applying Experimental Determined Kinetic Parameters to the Simulation of Vegetation Fire in the Fire Dynamics Simulator

Although intense wildfire research has been done in the US and in Australia, it cannot be transferred directly to the situation in Europe as the local vegetation has a significant influence on the fire spread. The EU-funded project TREEADS and the so-called German pilot within the project are concentrating on wildfire in Europe. Extensive experimental research is done on local vegetation in Germany and the experimental results are used to adjust the Fire Dynamics Simulator (FDS) to local vegetation as a fuel in the calculations. The particle model and the boundary fuel model are developed for the simulation of forest fires. Both models require the kinetic input for the dehydration, pyrolysis, and char oxidation process. This three-step simplified model describes the basic fuel combustion kinetic. Most published simulations use the default kinetic input of pine needles from FDS user manual.To adjust the simulation to local vegetation, the corresponding kinetic parameters have been experimental investigated. Samples of pine needles, moss and other falling leaves were collected, air dried and grinded into powder. The TG analysis of all these samples were done under different heating rate of 5, 10 and 20 K/min.The activation energy and the corresponding pre-exponential factor were calculated. The results show that fire spread depends significantly on the vegetation and comparison with small scale experiments show good agreement using the new kinetic parameters. The new model is applied to a larger scenario and will be compared to the results of large-scale experiments for further validation of the model.

Hongyi Wu, Anja Hofmann-Böllinghaus
Principles for Firefighting Assets Allocation. Integrating National and Regional Forest Fires Logs into the Vulnerability Analysis

Italian forest fire fighting assets include personnel, equipment, vehicles, helicopters and airplanes. The national resources are mainly represented by air-tankers and helicopters, deployed by the Unified Air Operations Center (COAU) upon regional request. Each Region is responsible to define its forest fire fighting response plan and establish a Permanent Unified Operations Command (SOUP), coordinating the intervention of aerial and ground firefighting assets. Each Region may establish an agreement with the Regional Firefighter’s Brigade to deploy an additional dedicated contingent of firefighters and vehicles during the forest fire campaign. Given this regulatory framework, it is difficult to get a comprehensive view of the aerial and ground forces deployed to fight forest fires integrated by the GIS mapping of their localizations and burned areas. This study is focused on the forest fire events occurred in the Lazio region, Italy, in the years 2019–2022. This integrated approach allows to conduct a systematic analysis of the conditions of use of the aerial and ground forces and provides a sound basis for further analysis, being the monitoring of the seasonal trends or the definition of firefighting asset allocations. Most of the forest fires recorded in the Lazio region is related to the human activity and any forest fire risk assessment should include their localization and frequency of occurrence.

Alberto Tinaburri, Fabio Alaimo Ponziani
Drone Swarm Technology as an Option to Suppress Forest Fires

This study used both practical and theoretical approach to investigate the possibility of drone usage delivering suppressant to fire front. Firstly, the required width of wetting strip and the required amount of water per unique area were investigated; practical experience shows that based on the flame length firefighters can estimate both the effective width of the firebreak and the amount of water required per a unique area. Second part of this paper, the transport capability of a drone was investigated during its life cycle that is specially optimized for firefighting. In the example author took a 100 kg transport capacity that is with multiplying easy to transfer to other drone design; in case of about 0.5 MWm−1 fire intensity 100 kg water is enough to make about 100 m long firebreak, in case of about 3.5 MWm−1 fire intensity it can create only 2.5 m firebreak. Even if this latest result seems a bit short, we have to take into account the swarm technology. In 10 km distance 30 drones can built a 5 m long firebreak per a minute that means 300 m per hour. This result is no worse than what large or very large air tankers can built averagely in this fire intensity.

Ágoston Restás
Water Source from Under Our Feet – Case Study at Homokhátság Area, Hungary

In case of long time wildfires, firefighters usually suffer from the lack of reliable water supply. One of the several reasons is obviously that most wildfires occur during periods of drought, when there is no rainfall and natural water sources locally available are low or missing. Another problem with the water supply is that the fire front and the water source are usually quite far apart. In this case, firefighters are faced with a logistical problem, where not only the limited number of fire trucks, but also the slow movement of these vehicles or even their getting stuck in rural terrain have to be taken into account. The Hungarian example of the Homokhátság area presented in this paper shows the use of a local opportunity, just as the smart use of groundwater can provide an adequate water source at the fire site. With regard to the effective water transport, the question arises as to whether the average water flow that can be provided during a conventional long-distance water transport can also be provided by the water flow of wells drilled on the fire site. In this example, drilled well can provide a flow rate of 400 lmin−1 in less than in 3 h after drilling has started. The research shows that, under certain conditions, groundwater supplied by drilled wells can provide an alternative solution to the logistical difficulties of long-distance water transport in a long-term firefighting operation.

Ágoston Restás, András Kristóf, Ágnes Süli, László Bodnár
Composition and Combustion: A Comprehensive Study of German Tree and Shrub Vegetation

Central European vegetation exhibits remarkable diversity in its horizontal structure, particularly within economically managed forests in Germany, where various tree species coexist with a variety of ground-level vegetation. While detailed spatial resolutions and representations of these prevalent vegetation types are available in various fuel maps, a comprehensive understanding of fuel composition in combination with typical combustion characteristics remains not available. This paper presents a comprehensive study that involves experimental investigations comprising elemental analysis, determination of heat of combustion and thermogravimetric analysis. These experiments were conducted on various types of trees (alder, oak, pine, spruce, larch, beech) and common ground vegetation (moss, reed grass, needles, cones) individually. The experimental analysis serves to describe the compositions of these materials, distinguishing between organic and inorganic components. Furthermore, the analysed samples are assessed for their heat of combustion and the characteristic thermal decomposition processes they undergo during the increase of temperatures.Subsequently, the collected data is systematically compared, resulting in an evaluation and classification of the vegetation. These findings offer valuable insights into the overall composition of this kind of fuels and and provide valuable insights into the combustion characteristics. The elemental analysis data serves as the reactants (educts) for formulation equations that characterize the composition of smoke gases released during combustion. Simultaneously, they can serve as a basis for fire spread models, for the containment and effective fighting of (wild)fires.

Lukas Heydick, Kira Piechnik, Andrea Klippel
Wood & Fire Safety 2024
Linda Makovická Osvaldová
Laura E. Hasburgh
Oisik Das
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