This study extends conventional life cycle assessment (LCA), which typically assumes an incident-free service life, to explicitly incorporate fire events and fire protection systems, enabling systematic quantification of their environmental consequences and mitigation effects in timber buildings. A proof-of-concept application was conducted for a timber-based residential compartment under four representative fire scenarios, ranging from minor object ignition to a fully developed enclosure fire, with and without sprinkler protection. Fire-related consequences were decomposed into combustion emissions, emergency response activities, and post-fire material replacement and integrated within a building LCA framework. The results show that fire development is the dominant driver of environmental burdens, with fully developed, non-sprinklered fires increasing impacts by more than 80% compared to small, confined fires. Material replacement emerged as the primary contributor, typically accounting for over 80% of total fire-related impacts, while direct combustion emissions played a comparatively minor role. Automatic sprinkler activation reduced total fire-related impacts by more than 85% across all indicators, while adding only 1-2% to the building's embodied impacts. These findings demonstrate that integrating fire scenarios into LCA enables a more realistic assessment of the environmental performance of timber buildings and supports informed decisions on lowcarbon fire safety strategies.

This paper presents a numerical and experimental study on stability until burnout of glued-laminated timber columns in compartment fires. In a previously reported experimental study, six 3.7 m long, 280 x 280 mm2 timber columns designed for 60 min of standard fire resistance failed to survive various compartment fires, with four of the six columns failing due to thermal wave penetration into the cross section during the decay phase of the fire. Here, six additional compartment fire tests are conducted, supported by numerical simulations, to investigate the design of timber columns for burnout resistance. A finite element model is used to design the size of the columns to mitigate the effect of the thermal wave. Five tests on columns up to 400 x 400 mm2 show that increasing the section size at constant loading enhances fire endurance, but the columns later failed due to local smoldering. While failure in the smaller columns was driven by the thermal wave and occurred within two hours of ignition, failure in the larger columns was caused by smoldering and occurred more than 10 h after ignition. In a sixth test, on a 280 x 280 mm2 column, water-based fire suppression was used 35 min after ignition. The column remained stable until burnout, showing that early fire suppression may prevent failure of timber columns by addressing both the thermal wave and smoldering mechanisms.

Timber framing is increasingly used as a load-bearing structural system in mid-rise and high-rise buildings. While extensive data exists from standard furnace tests, there is a lack of data on the fire performance of loaded timber members in full-scale compartment fires. Compartment fire tests are crucial to investigate a structure's performance under conditions where the fire is let to grow naturally with the fuel and oxygen present in the room and then let to cool down as the fuel burns out. This paper presents the findings from six fire tests performed on glue laminated timber columns in a custom-built compartment. Wood cribs are used as fuel. The columns, 3680 mm long with a 280 x 280 mm2 section, are subjected to constant axial loading during the whole fire duration. Column design and loading are based on a 60-min fire resistance. The tests vary in opening factor, fire load, and wood crib size. Column failure was observed in the six tests, with failure times ranging from 35 to 71 min. In four of the tests, failure occurred after the gas temperature had started to cool down. Comparisons with tests on similar columns made in a fire resistance furnace allow comparing charring rates observed in standard conditions and in natural fires.

This paper presents the data and the results of seven fire tests performed on glue laminated timber columns in a compartment built especially for the tests and in which timber wood cribs created a so-called natural fire.These tests are part of a research programme titled "burnout resistance" to establish a new methodology to better describe performance of structural elements during the whole duration of a fire.Comparisons with similar tests made in a fire resistance furnace allow comparing charring rates observed in standard conditions and in natural fires.

This paper presents the results of an experimental campaign designed to compare and understand the performance of passive protection under exposure to standard furnace tests and natural fires.As part of this campaign, five natural fire experiments were performed with partially protected cross-laminated timber (CLT) compartments under a range of ventilation conditions.In all the tests, only one side wall was left completely unprotected, and all other timber surfaces were protected with either two layers of 18 mm standard gypsum boards (GB) or two layers of 25 mm standard GBs.The structural CLT ceilings were subjected to a superimposed dead load of 1.35 kN/m² during the natural fire tests, and the fire load was (on average) 950 MJ/m²; chosen to represent the Eurocode 1991-1-2 characteristic value for dwellings.The performance of the passive protection was mainly evaluated with regards to the time to reach a protected timber surface temperature of 250°C.The testing confirms that the resulting fire protection performance of a given gypsum board layout depends on the ventilation conditions of the fire compartment, with more severe (and closest to ISO testing) outcomes when testing under ventilation-controlled scenarios.This paper provides data that sheds light on the co-dependency of the passive protection design and compartment fire dynamics and underlines the importance of considering the safety objectives of a building when defining the performance criteria of its structural elements.

The recommendation is based on the co-authors’ work organized by the RILEM TC 256-SPF “Spalling of concrete due to fire: testing and modelling”. The Committee has defined two types of screening tests for characterization of concrete propensity to fire spalling: Material screening tests and Product screening tests. Definitions of both types of tests are given in the paper. The following recommendations apply to Material screening tests. The material screening tests described in these recommendations are a set of minimum requirements to test concrete spalling propensity (for example, the minimal specimen size). This document covers the aspects of concrete characterization, specimen geometries, storage conditions, test methods and measured parameters.

The recommendation is based on the co-authors’ work organized by the RILEM TC 256-SPF “Spalling of concrete due to fire: testing and modelling”. It aims to provide useful information, guidance and best practices in fire spalling assessment to laboratories that perform large-scale tests based on fire resistance test standards. It provides guidance on the spalling observation techniques during testing, as well as post-test spalling quantification/assessment methods. This document is intended to be used in conjunction with the fire resistance test standards, e.g. EN 1363-1 and ISO 834-1.

Post‐flashover fires inherently lead to external fire plumes, constituting a hazard for rapid fire spread over façades. As multi‐storey mass timber buildings with internal visible timber surfaces become more common, there are concerns that such buildings would produce larger external plumes and hazards (assuming all other parameters equal). The literature reveals only indications of this, and how the actual exposure relates to different test methods for assessment is unknown. Here we utilise a series of full‐scale mass timber compartment tests to quantify the exposure to the external façade. An incombustible external façade is instrumented with gauges at positions corresponding to reference data from several different assessment methods. The results show that there is an increase in plume duration, height, and temperatures when increasing the areas of exposed timber, but that this increase is less for normal‐ to large‐opening compartments, than was previously seen in small‐opening compartments. Also, normal variations in external wind speed have a larger influence on plume heights than the effect of doubling exposed timber surfaces. Test methods used for regulatory compliance differ significantly not only in exposure but also in pass/fail criteria. The proposed European large exposure method and the BS8414 method exhibit exposures on par with the severe end of what could be expected from mass timber compartments, whereas methods like SP Fire 105 and Lepir II produce significantly less severe plumes. However, the safety level is always a combination of exposure and assessment criteria. This data can help justify assessment criteria from a performance perspective.

This special issue of Fire and Materials presents global research into timber structures and fire safety. This follows the renewed momentum in sustainable timber design in the 21st century. Contemporary practitioners and researchers are tasked with a need for information into the fire safety of these structures and from a sustainability point of view, important combination of timber and other structures (Figure 1). The special issue was conceived in late 2020. A call for papers was issued in 2021 and advertised on many different social mediabased platforms. Practitioners and researchers were invited to submit contributions to gather the state of the art on the subject intended to help guide critical research gaps. Specifically, the following areas were identified for interest in this issue: compartment fire evolution, structural resilience, adhesives and other components of construction, code and design method development, underlying mechanisms of timber degradation (charring, pyrolysis, moisture transport and loss, etc.), useful applications of research in practice, and so as not to restrict papers significantly the issue was open to relevant topics proposed by the submitting authors. Eleven papers were ultimately accepted. It must be recognized the substantial efforts of all authors herein who faced extraordinary times in completing these studies that are presented in this special issue. Specific acknowledgement being those to our graduate student authors who experienced significant challenges in their studies and academic development during the COVID-19 pandemic. The resulting collection of papers does not just capture the badly needed research for the subject, but the issue recognizes the perseverance of these researchers in addressing this critical need for our society to produce and maintain safe and sustainable timber structures. The editorial team on this special issue also recognizes the valuable contributions made by the reviewers for this special issue as per anonymity are not named. These reviewer's feedback and acceptance to review articles made this issue the success it has been and allowed a timely production by 2023. These papers within the special issue are described below with specific reference to their novelty and practical use. The first article includes a review of 63 compartment fire tests including timber structures regarding temperature development and charring behaviour. In the reviewed material, timber ceilings had on average a 16% lower charring rate than timber walls and the peak temperatures in most experiments were higher than non-combustible compartments. The second article includes a comparison of the thermal exposure from external fire plumes in compartment fire tests with façade test methods used in Europe including the European test methodology under development. In the compartment tests, between 43% and 78% of the surfaces were exposed mass timber. The main conclusion was that the thermal exposure from the external fire plumes corresponded best with the British BS8414 façade fire testing method and the European test method under development. Timber columns may fail in the cooling phase of a fire scenario. This was explored by using the duration of heating phase methodology, DHP. This research showed experimentally that the columns tested failed during the cooling phase after exposure to fire for which the heating phase lasted about 25% of the standard fire resistance of the columns. This was shown to be in line with a previous numerical study. Modelling of timber structural members exposed to realistic fire impact was developed and explored using the Open Seas platform. The model enables modelling the heat transfer of timber sections in non-standard fire scenarios and thermo-mechanical analysis for various timber structural members. This paper presents experiments on identical timber beam–column subassemblies exposed to the same heating duration but with two F IGURE 1 Contemporary corridor of a leisure facility in Canada using engineered wood as its ceiling (Author's photo). Received: 15 March 2023 Accepted: 15 March 2023

This paper describes fire tests on loaded glued laminated timber columns in which the structural response was measured during the heating and cooling phases. Identical columns with 280 × 280 mm 2 cross-section and 3.7 m length were tested under various heating durations in a standard furnace to investigate integrity to full burnout. Two of the columns were subjected to ISO 834 heating until failure and their measured fire resistance was 55 and 58 min, respectively. Two columns were subjected to 15 min of ISO 834 heating followed by controlled cooling; these columns failed during the cooling phase, respectively after 98 and 153 min. Flame self-extinction occurred after approximately 40 min while smoldering continued locally. Two columns tested under 10 min of ISO 834 heating both survived the defined heating–cooling exposure. Thermocouples inside the columns show sustained temperature increases for hours after the end of the heating phase. These full-scale furnace experiments show that timber columns may fail during the cooling phase after exposure to standard heating for about 25% of the standard fire resistance duration. These results, in line with previous numerical predictions, highlight the need for further investigation into fire safety until full burnout for timber structures.

Structures may collapse during the cooling phase of a fire, yet standard furnace tests only measure the response under heating. There lacks experimental test protocols and design methods to assess resistance until burnout. This paper describes a new experimental approach for burnout resistance evaluation, reports experimental data on loaded reinforced concrete columns in furnace tests with cooling down phases, and presents numerical models of the tests. The test results show that columns designed for a standard fire resistance of 60 min exhibited a fire resistance of 83 min in the furnace but failed during the cooling phase when the burners were shut off after 72 min while the load was maintained. Two other specimens survived exposure to heating of 45 and 55 min, respectively, and their residual capacity was measured. Finite element analyses show agreement with the tests, showing applicability of numerical methods for evaluating burnout resistance of concrete columns. These findings demonstrate experimentally that delayed thermal-mechanical effects can jeopardize structural stability in real fires, and provide a framework to measure these effects. Moving beyond fire resistance to quantify the response until burnout will support designs for safety of occupants and firefighters throughout the fire and promote repairability and resilience.

The environmental impact from enclosure fires is explored in this chapter. Main influencing parameters that are discussed are (i) fire dynamics, (ii) the incident response and the (iii) post-fire remediation activities. In this chapter, the discussion of fire dynamics includes the influence of the enclosure on the fire growth, and the influence of the combustion conditions, compartment size and fire loads on the fully developed fire. Incident response is considered in order to understand the impact of response tactics including time of extinguishment, amount and type of suppressant on the overall environmental impact of the fire, together with other environmental impacts from the fire and rescue service. The third influencing parameter on the environmental impact from enclosure fires, post-fire remediation, deals with the environmental impact from replacement of materials and structures including restoration of the fire site. It is noted that this last factor can be significant and is often overlooked. Finally, the application of life cycle thinking to sprinkler systems in enclosures, and fires including industrial chemicals are discussed briefly in this chapter.

Concrete spalling is an important phenomenon to consider when evaluating the fire behavior of concrete, as this can sometimes have an impact on the structural capacity of the studied element. Spalling can be assessed experimentally using screening tests although it is influenced by the size, geometry, and boundary conditions of the tested element, among other factors. No standardized and systematic methods are yet available to assess concrete spalling sensitivity by testing. Plus, comparative results between screenings tests (small and medium scale) and full-scale tests to evaluate their representativity remain scarce in the literature. In this study, five different spalling tests-with different geometries and boundary conditions-that are used as screening tests were investigated. A concrete mix known to be sensitive to spalling was used to evaluate the representativity of two types of screening tests (material screening tests and intermediate-scale screening tests). The representativity of these test setups was evaluated by comparing the measured spalling depths to the spalling measured on a full-scale slab test using the same concrete mix. This comparative study confirmed that the presence of load and/or restraint was essential for a good representativity for a screening test but should always be implemented in large enough specimens.

SummaryAn experimental study of the influence of an exposed combustible ceiling on compartment fire dynamics has been performed. The fire dynamics in compartments with combustible cross‐laminated timber ceilings vs non‐combustible reinforced concrete ceilings in otherwise identical compartments with three different ventilation factors were investigated. The experimental results are compared against predictions from two theoretical models for compartment fire dynamics: (a) the parametric fire model given in EN 1991‐1‐2, and (b) a model developed at Technische Universität Braunschweig, which are the parametric fire models currently used in Germany. It is confirmed that the introduction of a combustible timber ceiling leads to higher temperatures within the enclosure, both under fuel‐controlled and ventilation‐controlled scenarios. It is also demonstrated that the theoretical models considered in this article require refinement in order to adequately represent all relevant scenarios when combustible ceilings are present. A refinement of the German model, by adding the fuel from the combustible ceiling to the occupancy fuel load, was shown to not adequately capture the response for the ventilation‐controlled fires.

Since 1979, the Interflam conference series has been one of the leading conferences, which focus on the most contemporary fire safety research topics. An inspection of previous proceedings exemplifies this as the conference evolved to include many subjects that matured in the field and represent the contributions in a platform where results and analysis could be timely shared.1 Fire resistance as a specific topic has always had a presence in Interflam. However, it was not until the early 1990s that the topic came to fruition. For example, in the first decade of the conference, only six articles were presented on the topic of fire resistance. Since the inclusion of a critical analysis of the then conducted steel framed Cardington test series by 1996, nearly 100 full articles on the topic of fire resistance have appeared in Interflam proceedings. That test series was a fundamental turning point for how fire resistance of structures is considered and for the creation of computational tools used for structural fire design. By 1999, the Interflam conference series featured full sessions on related fire resistance topics. Today, this special issue recognizes the diversity of the topics that differentiate from steel-only focuses and feature a range of contemporary issues. Mass timber, for example, began to emerge as a separate topic branching distinctly from fire resistance alone. This issue of Fire and Materials features 10 articles prepared and reviewed in greater detail than their counterparts received at Interflam in 2019. The first five articles in this special issue focus on various aspects of fire performance of timber construction. The first article reports the results of an experimental study in which the effect on compartment fire severity of a cross-laminated timber (CLT) ceiling vs a reinforced concrete ceiling was investigated.2 The study confirms that the use of a combustible timber ceiling results in higher temperatures within the enclosure, regardless of whether the fire is fuel or ventilation controlled. The article further demonstrates that methods to estimate the fully developed fire temperatures in a compartment of noncombustible construction require refinement to obtain accurate temperature predictions when a combustible ceiling is present. The work described in the second article was motivated by the large scatter in the tensile strength data at elevated temperatures for wood reported in the literature.3 Steady-state tensile strength experiments below charring temperatures were performed. The results were then used to assess the tensile strength of a wooden beam subjected to a fire using Fire Dynamics Simulator. The third article focuses on the thermo-mechanical behavior of CLT slabs under standard and natural fire exposure conditions.4 Experimental data are presented that provide new insights into the behavior of unprotected CLT slabs exposed to fire. A detailed analysis of the thermo-mechanical performance of the slabs leads to a better understanding of mechanical failure during and after fire exposure. The last two articles on timber construction deal with the use of gypsum board as a protective membrane. Chorlton et al describe the results of a two-stage experimental program with the purpose of understanding multilayered encapsulation performance of timber columns exposed in nonstandard fires that include a natural cooling phase.5 The first stage involved a timber column protected with fire-rated gypsum board exposed to a fire within a large, open farm structure from ignition to burnout and cool down. The test showed that three layers of 15.9 mm Type X gypsum board were insufficient to protect the column. The second stage of the research involved four laboratory experiments in which one face of an encapsulated timber column was exposed to a methanol pool fire. These tests imply that timber elements can be adequately protected from fire exposure, provided the screw spacing is strictly adhered to and redundant layers of gypsum are installed. The final article on timber construction presents the results of seven standard fire resistance tests on wood frame wall assemblies.6 The study examined the effect of insulation (cellulosic, glass, and rock fiber), wood stud spacing, and mid-height blocking on the fire resistance of protected interior wall assemblies with a single or double row of wood studs. This special issue also includes three articles related to fire resistance of concrete. The first article illustrates the use of probabilistic methods for demonstrating adequate safety in the framework of British Standard PD 7974-7:2019.7 Three different approaches to determine an absolute safety target for a concrete column in an office building are explained. The two subsequent articles concern the fire spalling of concrete. An innovative material screening test method, with concrete molded in steel pipes to create a restraint during testing, is illustrated using a comparative study.8 This seems to be a promising test setup, although it appears that the size of the specimen is critical. In the second article on fire spalling of concrete, it is shown that addition of even relatively small amounts of polypropylene fiber to the fresh concrete mix can reduce fire spalling.9 This study also presents findings indicating that small unloaded concrete cubes exposed to the same heating as large loaded slabs exhibit no spalling, while some equivalent large slabs spalled beyond the layer of reinforcement. This demonstrates once again that tests based on small, unloaded specimens are not relevant when assessing fire spalling of larger cross-sections loaded in compression. Novel experimental studies that extend the study of materials beyond standardized test specifications are also considered in the issue. This includes an experimental study using the novel heat-transfer rate inducing system test method, which considered the influence of substrate thermal conditions on the behavior of thin intumescent coatings.10 The substrate thermal conditions were found to govern the swelling of intumescent coatings and, therefore, their effectiveness in protecting load-bearing structural elements. A separate study also examined partitions and scale effects.11 In this study, the influence of height of glazed partitions with fire resistance tests that exceed the dimensions of the sample walls was considered. The study concluded that the height of the partition does not have a significant impact on its insulation and integrity subjected to limitations on the size of the glass panes, symmetry, and stiffening of mullions.

SummaryThe results presented in this paper are part of a multi‐partner collaborative project named ‘The Épernon Fire Tests Programme’, the purpose of which is to analyse the different behaviours of combustible and non‐combustible loaded structures when they are tested under standard and ‘natural’ fires. The project has several objectives, such as quantification of the energy participation of combustible materials in fire tests, the influence of combustible surfaces and ventilation factors on the dynamics of compartment fires, and the thermo‐mechanical behaviour of concrete and timber elements under natural fires. This paper focuses on the thermo‐mechanical behaviour of cross‐laminated timber (CLT) slabs under standard and natural fires. The objective is to provide new experimental data on the behaviour of unprotected CLT slabs exposed to fire. In addition, we present a detailed analysis of the thermo‐mechanical behaviour of the slabs, particularly aimed at better understanding the mechanical failures of some of the slabs during and after fire exposure.

As in many countries, the Swedish building regulation is constantly updated. In most cases, these updates are small and do not affect the overall structure of the building code. However, from time to time, larger changes are made and the framework of how to use the code is changed. The latest of these major changes was made in 2011 and the code is since then a mix of performance-based and prescriptive requirements. During 2016, a study was initiated with the purpose to get the Swedish fire safety industry's perspective on the current structure of the Swedish building code and how the code should be developed in the future. This study concludes that there are substantial differences within the fire safety industry on the view of the building code. Both on the state of the current code and on how the code should develop in the future. However, in some points, the majority of the participants agree, for example, most participants think that the control system for ensuring fire safety should be expanded, both in the design and in the construction phase.

Nine participants, representing eight different Swedish fire consultancy firms participated in a Round Robin study where two different cases were simulated with the Fire Dynamics Simulator. The first case included a large open warehouse where the activation of a sprinkler system was to be studied. In the second case time to critical conditions in a theatre was to be calculated. The participants were given clear instructions on the building layout and heat release rate for the two cases. Still, the results demonstrate a significant variation in time to sprinkler system activation (range of 110 seconds) and available safe escape time (range of 60 seconds), between the participants. It is important to emphasise that some degree of variation is unavoidable, as engineers can model things differently without the modelling solution necessarily being incorrect. Even though it is hard to isolate and specific cause of the variation, some of the variation seen in this study is related to modelling choices that are questionable and consequently problematic for the reliability of the fire safety design.

SummaryThe addition of polypropylene (PP) fibres has been shown to reduce the fire spalling propensity of concrete. When including this type of fibres in the concrete, the concrete mix becomes less robust, and small deviations in the constitutes change the workability and properties of the concrete. So, from a manufacturing perspective as small dosages as possible of PP fibres are desirable. Very few large‐scale fire resistance tests of concrete loaded in compression exist showing the function of PP fibres at low dosages on concrete mixes sensitive to spalling if no fibres are added. In this paper, results from 26 fire tests are presented and analysed. The test results are from four different experimental campaigns, but all the mixes have in common that the water‐to‐cement ratio is 0.40. The results show that an amount of only 0.6 kg/m3 PP fibres has a significant effect on the spalling propensity and that even lower amounts reduce the spalling although they do not eliminate it entirely. During one of the fire tests on large slabs loaded in compression, unloaded small cubes of the same mixes were also included in the furnace. None of the small specimens spalled, whereas some of the corresponding large slabs spalled beyond the layer of reinforcement. This illustrates that tests on small, unloaded specimens are not relevant when assessing fire spalling of larger cross‐sections loaded in compression.

In Sweden the responsibility for environmental damage when emergency responders are called to an incident is increasingly focussing on the responders. The problem is that most incident response personnel do not have the training and expertise to assess the environmental consequences of their suppression operations. The Fire Impact Tool was developed for training responders about how fire effluents and suppression media affect air, surface/ groundwater and soil. The tool has three interdependent parts: fire models (for vehicles and enclosures), an environmental risk assessment (ERA) model for local impacts, and a life cycle assessment (LCA) model for global impacts. Users can create two scenarios that are compared with a reference case in which responders arrive at the incident and prevent the fire from spreading beyond the vehicle or enclosure but do not suppress the fire. The Fire Impact Tool is not intended for use during an actual fire incident. This work does not answer every question for every possible fire scenario, but it does provide a framework for deeper, broader, more comprehensive training and pre-planning. This is a necessary step toward a future in which responders are prepared to make informed decisions about firefighting strategies and tactics that include environmental consequences.