In Mohaine et al.,1 the following errors were published. Figure 12 was incorrectly drawn. Unloaded slab ISS_C_0 and Loaded slab ISS_C_0,75 correspond to the “time of onset of spalling” rather to the “maximum spalling depth” of the slabs. The correct figure 12 is shown as below. The correct figure was presented in the Interflam 2019 conference paper “Cross-comparison of screening tests for concrete spalling”, Mohaine S., Robert F., Boström L., Lion M. and McNamee R., Interflam Conference, 1-3 July 2019, Windsor, UK”. The authors apologize for the error. REFERENCE 1. Mohaine S, Boström L, Lion M, McNamee R, Robert F. Cross-comparison of screening tests for fire spalling of concrete. Fire Mater 2021;45:929-942. doi:10.1002/fam.2946

This paper deals with the bulk density determination of char, which is an important input parameter for numerical simulations of pyrolysis. The aim was to develop a time and cost-effective, non-destructive, and repeatable method capable to determine the bulk density of highly porous, fragile wood and engineered wood samples of various shapes, namely char of spruce and oriented strand board. Char samples were prepared in a cone calorimeter under various heat flux exposures. Photogrammetry was chosen for this purpose. A detailed photogrammetric measurement procedure consisting of sample preparation, sample measurement and software reconstruction was designed and validated. It was found that the bulk density of char depends on the virgin material and the way char was formed. The spruce and oriented strand board char bulk density value is provided to be used in pyrolysis modeling and compared to literature.

To study the effect of thickness on the fire spreading characteristics of aluminum composite panels, a reduced-scale test bench was built to simulate the development of an overflow fire in a high-rise building. Analysis of the fire spreading characteristics was performed in terms of the flame shape, flame height, fire spread rate, and temperature change. Then, an Fire Dynamics Simulatior model was established to verify the accuracy of the experiment using numerical simulations. The results showed that the flame shape of the 3 and 4 mm aluminum composite panels was a triangular cone, while the flame shape of the 5 and 6 mm aluminum composite panels was approximately rectangular. By establishing the dimensionless flame height, the flame height increased with the panel thickness. The fire spread rate of the aluminum composite panels increased first and then decreased upon increasing the thickness, which was consistent with the simulation results. The temperature change curves all showed a rapid initial increase and then a stable temperature in the later period. The simulation results conformed well to the experimental results.

The toxicity and density of smoke from 10 commonly used commercial polymer types was studied using the European railway standard EN 45545-2. This test method was chosen because it reflects the current state-of-the-art in assessing the hazards of smoke in bench-scale test scenarios (not because of a specific link to railway applications). The study involves 72 commercially relevant formulations provided by 12 industrial companies. Polymers studied include PE, PP, PC, PA6, PA66, u-PVC, p-PVC, PU, PIR, and epoxy resins. Reference samples as well as samples containing halogenated and Phosphorus, Inorganic or Nitrogen based Flame Retardants (PIN FRs) were tested according to the French tubular furnace method (NF X 70-100) to evaluate their smoke toxicity at 600°C and according to ISO 5659-2 at 50 kW m−2 with Annex C of EN 45545-2 to evaluate their smoke density as well as toxicity at 4 and 8 min. This study highlights that the measured toxicity and calculated Conventional Indexes of Toxicity (CITNLP, CIT4 min, CIT8 min), as well as maximum smoke density (DsMAX) show generally no significant increase in the presence of PIN FRs in comparison to the neat polymers. The use of intumescent FRs or hydroxide based FRs generally allows considerable smoke reduction with little impact on smoke toxicity. Bromine based-FRs were found to be detrimental to both hazards in most matrices studied here.

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). FIGURE 1Open in figure viewerPowerPoint Contemporary corridor of a leisure facility in Canada using engineered wood as its ceiling (Author's photo). The special issue was conceived in late 2020. A call for papers was issued in 2021 and advertised on many different social media-based 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.1 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.2 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.3 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.4 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 paper5 presents experiments on identical timber beam–column subassemblies exposed to the same heating duration but with two different cooling phases. It addresses how thermal fields develop in timber connections during the cooling phase of fires and what influence different cooling rates may have. The results therein showed that exposed steel components conduct heat into the main connection system, which then propagated as a thermal wave through the timber elements. Researchers also investigated the thermal mechanisms behind the appearance of the second heat release rate peak of spruce materials when a cone apparatus is utilized for testing.6 They discuss the governing tests conditions behind this second peak. In a paper on smouldering ignition of wood, three different regimes were identified: (i) no ignition, (ii) un-sustained smouldering and (iii) self-sustained smouldering.7 In the experimental campaign on beech woods, minimum radiant heat flux for smouldering ignition was about 5.5 kW/m2 after long time exposure. A criterion for self-sustained smouldering, when smouldering continuous without irradiation, was set to (i) a minimum surface temperature of 350 ± 20°C, (ii) a minimum smouldering front thickness of 30 ± 5 mm and (iii) a minimum mass flux of 3.8 ± 0.4 g/m2 s. A framework is also presented for using building information modelling (BIM) with fire dynamics simulation (FDS) to simulate the fire behaviour of a CLT compartment that would be under construction.8 An IFC model language is used for the data transfer between BIM viewing software and PyroSim. This simulation is validated against a real experiment of a medium-sized CLT compartment with various exposed surfaces and the framework is used to decide which walls or ceiling should be protected while under construction. The authors call for more benchmarking with various sized compartments. The last set of papers is a three-part series9-11 that addresses that current experimental fire research for timber is generally limited to small compartments (<100 m2). These three papers feature a series of experiments, known as CodeRed, in a facility of 352 m2 that was built in France to examine the influence of timber on fire dynamics of large open-plan compartments. In CodeRed #01,9 the impact of a timber ceiling on the fire dynamics was investigated. In CodeRed #02,10 the impact of ventilation was examined by halving the available ventilation. In CodeRed #04,11 the impact of exposed surface of the timber ceiling was investigated by encapsulating 50% of the ceiling. CodeRed #03 was related to the impact of water mist, not a fire dynamics experiment, and hence not part of this special issue and published elsewhere.

The use of mass timber in construction is becoming a compelling option when faced with the high carbon footprint of traditional concrete and steel production. However, fire safety standards are yet to evolve to support these designs. Encapsulation is commonly used to protect all, or some, of the timber surfaces and reduce the risks introduced. This paper presents the results from CodeRed #04, the final experiment of the CodeRed experimental campaign. This experiment was carried out inside a purpose-built facility to capture fire dynamics in large compartments with exposed timber. CodeRed #04 had identical characteristics to CodeRed #01 with the exception that ~50% of the cross-laminated timber (CLT) ceiling was encapsulated. The experiments were intentionally similar to the traveling fire experiments, x-ONE and x-TWO, which had a non-combustible ceiling to enable a direct comparison. The overall fire dynamics experienced in CodeRed #04, intersect the characteristics observed in CodeRed #01 and x-ONE and x-TWO.1. In CodeRed #04, there was a delay in the ignition of the CLT ceiling as the CLT directly above the crib was encapsulated. Once the CLT ceiling ignited, the fire spread rapidly throughout the compartment. The peak heat release rate (HRR) was estimated to be approximately 100 MW, a 17% decrease from CodeRed #01. Following CLT ignition the resulting fire duration, maximum temperatures, and heat fluxes were broadly similar to CodeRed #01. Flame heights of approximately 1.5 m were observed from the windows while flame heights of 2.5–3 m were observed in CodeRed #01. Therefore, flame heights were found to be comparable to x-TWO.1, though over a greater number of windows, reflecting the greater extent of simultaneous burning within the compartment. The average charring depth of the exposed CLT panels was ~25 mm, which is similar to that measured in CodeRed #01-suggesting that the fire severity near the ceiling was not strongly impacted by the 50% encapsulation of timber. No charring was observed where the ceiling was encapsulated and loaded service fixings installed through the encapsulation were found to be less likely to fail than when attached directly to the exposed timber. Smoldering was observed after the cessation of flaming and, in a few locations, was observed to progress through the thickness of the CLT panel and continue behind the encapsulation. This illustrates that, while encapsulation can succcessfully prevent flaming, it cannot be completely relied on to avoid smouldering. The findings from CodeRed #04 contribute to the development of evidence-based fire safety design methodologies for exposed mass timber buildings.

This paper assesses the capability of using a new data-driven approach to predict the bond strength between steel rebar and concrete subjected to high temperatures. The analysis has been conducted using a novel evolutionary polynomial regression analysis (EPR-MOGA) that employs soft computing techniques, and new correlations have been proposed. The proposed correlations provide better predictions and enhanced accuracy than existing approaches, such as classical regression analysis. Based on this novel approach, the resulting correlations have achieved a lower mean absolute error ( MAE $$ MAE $$ ), and root mean square error ( RMSE $$ RMSE $$ ), a mean ( μ $$ \mu $$ ) close to the optimum value (1.0) and a higher coefficient of determination (R2) compared to available correlations, which use classical regression analysis. Based on their enhanced performance, the proposed correlations can be used to obtain better optimised and more robust design calculations.

RP-3 aviation kerosene is a standard fuel that is used in civil aircraft and is a substitute for Jet-A fuel. This paper investigates the combustion behaviour of RP-3 aviation kerosene in an open space in the low-pressure environment of a plateau. A series of large-scale pools with diameters ranging from 0.4 m to 2.82 m combustion experiments are performed. Typical combustion characteristic parameters, including combustion rate, flame height and axial plume temperature distribution is measured. Results show that a low-pressure environment significantly affects pool fires. With combustion rate, there is a linear variation law between oil pool size and combustion rate. The experimental data are fitted as a means of obtaining the large-scale combustion rate relationship equation at low pressure. Experimental flame height data is compared using classical prediction models. Prediction model coefficients at low pressure are determined. The axial plume temperature distribution is greater than in the literature findings due to flames becoming longer in a low-pressure environment. The three regimes in McCaffery's model are redefined and correlate well with the vertical temperature profile of the pool centreline. The results of the experimental investigation will help research fire hazards in low-pressure environments while also contributing to the provision of basic data for the development of firefighting operation strategies.

The international standard ISO 5660 Cone Calorimeter test is widely used in fire research and for modeling, but not so often in legislation or requirements on products. The available acceptance criteria for products in different countries and codes have therefore been compiled and are presented in tables. Some research studies have also been included. There are several national standards with different designation based on ISO 5660 for fire testing according to the Cone Calorimeter, for example, ASTM E1354 in the US, AS/NZS 3837 in Australia, and New Zealand. ISO 5660 Reaction-to-fire is a small-scale test method and contains four parts: Heat release, smoke production, and mass loss rate Smoke production rate (dynamic measurement) Guidance on measurement Measurement of heat release for determination of low levels of combustibility Part 1 is most used and heat exposure at 50 kW/m2 is preferred in research and for expressing acceptance criteria, see Table 1. In a few cases, heat exposure at 25 kW/m2 is utilized, see Table 2. Part 4 uses a larger cone heater and allows larger specimens 150 × 150 mm compared to 100 × 100 mm for the other parts. National versions of ISO 5660-4 are used in Canada as CAN/ULC-S135 and in the US as ASTM E2965. TABLE 1. Acceptance criteria according to the Cone Calorimeter (ISO 5660-1 or equivalent test methods) at 50 kW/m2 used in codes and national regulations Country/Code Weathering method Acceptance criteria Used for Time to ignition, s Max HRR peak, kW/m2 Max HRR average, kW/m2 Max THR, MJ/m2 Test time, min, min Europe EN 16755 - - 150 (30 s average) 20% increase compared to before weathering 10 min after ignition Fire retardant wood products Japan - - 200 - 8 20 Non-combustible products Japan - - 200 - 8 10 Quasi Non-combustible products Japan - - 200 - 8 5 Fire retardant products Korea - - 200 (except for  20% of thickness) Semi Non-combustible products Korea - - 200 (except for  20% of thickness) Fire retardant products IBC International Building Code - - 150 - 20 - Water resistive barriers IBC International Building Code - - 400 - - - Children´s play structures IFC International Fire Code - - 300 - - - Waste containers and similar NFPA 1 Fire Code - - 300 - - - Plastic rubbish containers NFPA 101 Life Safety Code - - 300 - - - Plastic rubbish containers NFPA 5000 Building Code - - 150 - 20 - Water resistive barriers New Zealand - - 150 - - External cladding B New Zealand ASTM D2898 modif. - 100 - 25 15 Fire retardant timber cladding IMO FTP (MSC 88/26/Add.2 - > 20 - < 60 (30 s average) < 20 20 Material for furniture and other components MiL-STD-2031 - < 65 < 50 (30 s average) Composite materials used in US Navy Australia - Indices based on Kokkala et al. Fire and Materials12 Wall and ceiling linings TABLE 2. Acceptance criteria according to the Cone Calorimeter (ISO 5660-1 or equivalent test methods) at 25 kW/m2 used in codes and national regulations Country Weathering method Acceptance criteria Used for Max HRR peak, kW/m2 Max THR, MJ/m2 Test time, min New Zealand - 100 - 15 External cladding A Australia ASTM D2898 modif. 100 60 (10 min after ignition) 10 min after ignition Bushfire resisting timber A separate standard on mass loss rate is also available as ISO 17554. It may be used for industry production control. Acceptance criteria for general classification of building products are used in New Zealand as direct test data, see Table 1. Australia uses indices based on Cone Calorimeter data, and direct test data only for Bushfire resisting timber, see Table 2. The codes IBC and IFC use acceptance criteria for special products like water resistive barriers, children's playground structures, and plastic rubbish containers. The same is true for the NFPA standards 1, 101 and 5000. In the European standard EN 16755 and in New Zealand, the Cone Calorimeter is used specifically for fire retardant treated wood products before and after weathering, see Table 1. The main parameter used in acceptance criteria is peak heat release rate (HRR) in kW/m2. For non-combustibility total heat release (THR) in MJ/m2 is added in Japan and Korea. Canada and NFPA 220 use THR for non-combustibility but measured at different heat exposures and slightly different cone heaters, see Table 3. TABLE 3. Acceptance criteria according to the Cone Calorimeter (ISO 5660-4 or equivalent test methods) at 50 or 75 kW/m2 for non-combustible products Country/Code Acceptance criteria Test standard Comments Heat exposure, kW/m2 Max HRR peak, kW/m2 Max THR, MJ/m2 Test time, min Canada - 3 Until no heat or smoke release CAN/ULC-S135 Same cone heater size as ISO 5660-1 50 NFPA 220 Types of construction 150 (except for <10 s) 8 20 ASTM E2965 Larger cone heater size than ISO 5660-1 75 Table 4 presents two research studies with the aim to determine acceptance criteria based on extensive fire testing. The study by Wade aimed at creating performance-based criteria and is used as background verification for the legislation in New Zealand and the one by Tsantaridis et al focused on wood products. TABLE 4. Suggested acceptance criteria according to the Cone Calorimeter (ISO 5660-1 or equivalent test methods) at 50 kW/m2 from research studies Paper Time to ignition, s Acceptance criteria Applicable to Max HRR peak, kW/m2 Max THR, MJ/m2 Test time, min Tsantaridis et al., Interflam 2010 ≥40 ≤100 (for ≥900 s from start of heat exposure) - Fire retardant wood products Euroclass B Tsantaridis et al., Interflam 2010 ≥30 ≤180 (for ≥900 s from start of heat exposure) - Fire retardant wood products Euroclass C Tsantaridis et al., Interflam 2010 ≥15 ≤250 (for ≥900 s from start of heat exposure) - Wood products Euroclass D 13 - 150 - 15 External claddings

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 mm2 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.

Heritage timber buildings are found worldwide and their irreplaceable nature makes them of high value. A common occurrence on heritage timber members is radial shrinkage cracks resulting from changing moisture contents over time. There is little information available that can be used to assess the fire performance of heritage timber members (which has unique differences from contemporary timber), and to the author's awareness, no information regarding how the presence of radial cracks affects the fire performance and char depth of a timber member. The purpose of this study is to provide an evaluation of the effects of radial cracking on the fire performance of timber members, including its effect on char depth, time to ignition, and residual strength. Full-scale heritage Pine timber members were procured from a 115-year-old building undergoing demolition and then subjected to a pool fire. Cracked samples were also extracted from the members and tested in a Cone Calorimeter apparatus relative to solid samples. It was found that the presence of cracks did allow for deeper charring with the full-scale tests showing 64% greater char depth in the cracked region and the Cone Calorimeter tests showing 29% greater char depth on the cracked samples. Four-point bending tests of the full-scale members subjected to a pool fire showed that the effect of the fire exposure and the cracks did not significantly impact the capacity of the members (7.2% difference) but reduced the stiffness as the ultimate deflection increased by 43%. These results can help to inform practitioners who encounter heritage timber members to more accurately assess the fire performance of the member, such that they can make informed decisions on the level of fire protection required. The study also provides methodologies for the collection of heritage timber test materials.

This paper presents a study on the structural behaviour of stainless steel profiles under fire conditions. An experimental campaign of three-point bending tests on rectangular hollow section beams of the grade 1.4301 (also known as 304) were conducted, considering both steady-state and transient state conditions. Prior to those tests, the mechanical characterization of the stainless steel was investigated. The constitutive laws obtained by tensile tests at high temperatures are compared with those recommended in Eurocode 3, whose respective material models were recently proposed for modifications, still requiring complete validation. In addition, numerical modelling of the bending tests has been performed afterwards achieving close approximation to the observed experimental results. Finally, analytical methods to predict the load-deflection behaviour are also presented. Good agreement between the considered methodologies was attained validating their application on the prediction of the fire behaviour of stainless steel beams.

To investigate the effects of under-clothing airflows on the thermal protection performance (TPP) and thermal aging of flame-retardant fabrics, we constructed an under-clothing air-gap ventilation device based on the TPP tester. This device can generate different levels of airflow velocities such as 0.17, 1.0, and 2.0 m/s. The flame-retardant fabrics were exposed to a heat flux of 30 kW/m2 to simulate an indoor fire scene. The impacts of under-clothing airflows on the heat transfer behaviors of fabrics were analyzed with the temperature rise measured by thermocouples. The thermal aging behavior of the fabric was investigated based on the outer-shell morphology, mass loss, and residual tensile strength. The results of this study indicated that the under-clothing airflow enhanced the TPP of flame-retardant fabric and the best TPP was achieved under the airflow of 1.0 m/s. Under-clothing airflow increased the post-thermal-exposure mass loss of the fabric but did not further decrease the tensile strength. Higher severity thermal aging occurred for 2.0 m/s airflow than for 1.0 m/s airflow. The findings of this study are important for TPP prediction for firefighters' clothing and will help optimize firefighters' clothing design.

Ammonium polyphosphate (APP), piperazine pyrophosphate (PAPP), and melamine cyanurate (MCA) were used as raw materials to develop an intumescent flame retardant system (IFRS) for polypropylene (PP). The synergistic flame retardancy among APP, PAPP, and MCA was explored. The effect of the proportion of APP, PAPP, and MCA on the IFRS flame-retardant performance was studied. For the range of samples tested, the IFRS with the proportion of PAPP, MCA, and APP at 4:1:7.5 showed the best flame retardancy. When the addition of PAPP/MCA/APP IFRS in PP was 20%, the prepared flame-retardant PP composite (PP-PMA-3) passed UL-94 V-0 rating. Moreover, the PP-PMA-3 total heat release (THR) decreased by 46.4% compared with PP-0. Meanwhile, PAPP/MCA/APP IFRS showed good smoke suppression performance because the total smoke production (TSP) of PP-PMA-3 decreased by 65.0% compared with PP-0. In addition, the high flame retardancy and the flame-retardant mechanism of the prepared IFRS was explained.

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.

Firebrands, or smoldering and/or flaming particles, are in fact the main culprit to destroy structures in large outdoor fires. A recent comprehensive review of firebrand combustion reported that deposition and subsequent accumulation processes remain largely unexplored. As part of this work, a series of experiments were undertaken to investigate firebrand deposition and accumulation processes in the National Research Institute of Fire and Disaster (NRIFD)'s wind facility. A reduced-scale firebrand generator was utilized, and various flow obstructions were placed downstream of these firebrand generators to better understand these complex deposition processes. Results of these investigations for multiple wind speeds, firebrand size and mass distributions, and obstacle placement are presented and discussed.

Sodium bicarbonate and potassium bicarbonate are commonly used as the bases of dry powder fire extinguishing agents. However, the choices of particle diameter and base are still not obvious, bringing difficulties to the design of fire extinguishing agents. Through the study on thermal decomposition kinetics, it was found that the smaller the particle size, the faster the decomposition rate of dry powder agents. For instance, if the D90 of sodium bicarbonate is reduced from 46.2 to 1 μm, the decomposition rate triples. As determined by thermal decomposition experiments, the residues after a fire could be bicarbonates, carbonates, and mixtures. The residue solutions' pH shows that carbonates are more alkaline than bicarbonates, and potassium salts are more alkaline than sodium salts. The corrosion tests on four common metals reveal that the residues of potassium bicarbonate after a fire could accelerate the electrochemical corrosion of metal surfaces, especially aluminum alloys. This research identifies the ideal particle diameter and supports the choice of alkali metal salts for the design of dry powder agents.

Wood is one of the longest-standing and sustainable construction and building materials, and has gained a new renaissance for high-rise buildings to achieve global carbon neutrality. However, wood can sustain both flaming and smoldering fires, and numerous timber structure fires have raised fire safety to be a public concern. This work investigates the smoldering ignition of wood blocks under long-lasting low-intensity irradiation and the robustness of smoldering fire after the removal of irradiation. We found a smoldering ignition map including three regimes, (i) no ignition, (ii) unsustained smoldering, and (iii) self-sustained smoldering. The minimum irradiation for smoldering ignition of wood is about 5.5 kW/m2 after heating for hours. Without sufficient and in-depth preheating, smoldering ignition cannot self-sustain without irradiation. The criteria for self-sustained smoldering on thick wood include the minimum surface temperature of 350 ± 20°C, the minimum smoldering front thickness of 30 ± 5 mm, and the minimum mass flux of 3.8 ± 0.4 g/m2 s before the irradiation is terminated. The CO/CO2 ratio of the smoldering wood under low irradiation varies between 0.1 and 0.2. This work helps evaluate the fire risk of wood materials and understand their burning behaviors under real fire scenarios.

An eco-friendly and bio-based ternary hybrid hydrogel consisting of carrageenan, vermiculite, and dimethyl methyl phosphate (DMMP) was prepared through a facile one-pot method. Rheological tests showed that this ternary hybrid hydrogel was a power-law fluid. The formulation of the ternary hybrid hydrogel was also screened, and the optimal formulation was found to be the ternary hybrid hydrogel containing 1 wt% carrageenan, 2 wt% DMMP, and 4 wt% vermiculite. Firefighting experiments showed that the ternary hybrid hydrogel could stop the chain reaction and rapidly reduce the temperature of combustion. Compared to water, the extinguishing time of the ternary hybrid hydrogel was shortened by 46.6%, and the volume consumed was reduced by 43.3%. The superior fire extinguishing efficiency of the ternary hybrid hydrogel could be attributed to the combined effect of each component: carrageenan provides viscosity, making the hydrogel firmly cover the burning surface; DMMP works as a free radical scavenger that can stop chain reactions; and vermiculite acts as a barrier layer, which helps to insulate air and heat and prevent resurgence. This work provides an environmentally-friendly, cost-effective, and bio-based hybrid hydrogel for firefighting.

During a fire, the load-carrying cross section of timber members will reduce due to charring. This article summarizes experimental investigations into the charring rate of different timber species under standard fire conditions, identifies material properties that contribute to the variations of char rates across the different species, and evaluates the applicability of prescribed charring rates to solid timber, cross-laminated timber (CLT), and glulam exposed to standard fires. Data from the literature showed that density had the greatest impact on charring rate. The charring rate of timber decreased with increasing density, particularly timber densities >700 kg/m3. Prescribed charring rates from current design standards provide reasonable estimates of the average charring rate of timber with densities <700 kg/m3 exposed to standard fire curves. A linear charring rate of 0.65 mm/min was found to be suitable for CLT and glulam exposed to a standard fire for up to 180 min if the CLT did not experience char fall-off. The National Design Specification nonlinear charring model may underestimate the char depth of glulam exposed to standard fire curves for longer than 60 min; however, the percent underestimation was small and limited data was available. The review demonstrated the need for data on the char depths of glulam and CLT exposed to standard fire curves for longer than 60 min and particularly for longer than 120 min.