Fire and Materials最新文献

This study investigates the composition of smoke gases in forest and vegetation samples to draw conclusions about the actual smoke gas composition during wildfires. The focus is particularly on regions with extensive pine forests, like in Eastern Germany. The relevance of smoke gases is well illustrated by the example of wildfires in Québec, influencing air quality in New York, in 2023. By employing a modified DIN tube furnace, a bench-scale test set-up, the research emphasizes the examination of smoke composition from tree species and ground cover, prioritizing gases while disregarding particles. Key smoke gases are identified as CO, CO₂, SO₂, HCN, C₃H₄O (acrolein) and CH₂O (formaldehyde) and their concentrations are compared with Acute Exposure Guideline Levels (AEGL) limits. Acknowledging the limitations of AEGL usage and the problem with direct quantitative comparison of toxicant concentrations (cf. ISO 29903-1:2020), the study highlights variations in smoke composition across different samples. The results of the studies reveal a significant disparity in CO concentration between dry and fresh pine needles. Frequently, the AEGLs of key gases are exceeded significantly. The elemental analysis of the barks indicates distinct differences in composition, reflecting in the concentrations of smoke gases. The ratio of 1 mole of substance turnover to the identified key components will be used to determine input parameters for the subsequent numerical simulation.

The National Research Council Canada conducted two major fire resistance studies on floor assemblies over the past two decades. Despite the publication of the experimental results, there is a lack of suggested guidelines for design practitioners and gaps for future research. Thus, this paper comprehensively reviews the fire resistance results of 85 full-scale floor tests, suggests design guidelines, and identifies research gaps. These efforts aim to enhance the understanding and support the potential improvement of the fire performance of floor assemblies. The review of the results covers the impact of various design parameters on the fire resistance of floor assemblies, such as framing type and spacing, insulation type, subfloor configuration, resilient channel spacing, number of gypsum board layers, and screw spacing from the board edge. Although the interaction of these factors is complex, some of them play significant roles in determining the overall fire resistance of floor assemblies. For instance, rock and cellulose insulation outperformed glass fibre, a wider resilient channel spacing lowered fire resistance, whilst an increased distance of screws from the board edge improved the fire resistance. More importantly, detailed explanations are provided for the influences these parameters exert on fire resistance. Following this detailed examination of the results, design guidelines are provided for practitioners' consideration. A comparison is made between the experimental results and predictions from the component additive methods in the Canadian and Euro Codes, demonstrating that both methods yield conservative results. Finally, this paper concludes by identifying research gaps and providing recommendations for future investigations, including the necessity of experimental studies on floor assemblies with new design configurations and the promising role of machine learning in fire resistance evaluation.

During the recycling process, waste plastic undergoes various processes that change its geometry. The thermal properties and fire behaviour of plastic in different geometries has not been widely studied. This paper aims to determine critical thermal properties of plastic pellets made of recycled plastic. For this paper, cone calorimeter tests of various volumes of recycled plastic pellets of low- and high-density polyethylene and polypropylene were conducted. During these tests, the heat release rate (HRR), mass loss rate and time-to-ignition were measured, thereafter the heat of combustion (HOC) was calculated. A calibration of suitable time-to-ignition equations is carried out. The average HRR is between 353 and 581 kW/m² with an external heat flux of 50 kW/m². The measured time-to-ignition values ranged between 27 s at 50 kW/m² and just more than 90 s at 25 kW/m². Values obtained analytically from the thermally thin time-to-ignition equations for these materials describe ignition well, which appears to be due to the particulate nature of the samples. The HOC (40–41 MJ/kg) shows good agreement with the HOC for virgin plastic found in literature. These properties can be used as a basis for material characterisation, and further testing will be done before using this as simulation inputs to determine how bulk stored plastic pellets will behave in the event of a fire.

Low-temperature chemical oxidation is the major driver of self-heating during storage of wood pellets and its kinetics is essential to describe the heat evolution. In the present work, isothermal microcalorimetry was used to characterize heat generation behavior of three types of wood pellets (pine, fir, and redwood pellets) at 30–70°C. The obtained data were employed to derive the kinetics of low-temperature oxidation by the peak power, iso-conversional method, and non-steady analysis. The consistency and applicability of the kinetics derived by the three methods were evaluated. Kinetic parameters determined by the peak power method were observed to match those from the iso-conversional method at lower conversions of the oxidation for heat generation. The kinetics derived by the iso-conversional method indicated the oxidation reactivity generally decreasing and activation energy increasing with the conversion because of O₂ consumption and reaction mechanism changing. With the impact of O₂ consumption considered separately, the kinetics from the non-steady analysis is capable of describing the evolution of heat power with the conversion and also consistent with that from the peak power method in describing intrinsic reactivity of pellet materials. The kinetics from the peak power and iso-conversional methods lump the impact of O₂ concentration with the reaction reactivity, suggesting their applications requiring additional models for connecting with O₂ consumption.

Simulating fire and evacuation scenarios is crucial for engineers to assess building safety during fire incidents. Accurate simulations require data on occupants' behaviors, particularly during the pre-evacuation phase as these decisions significantly impact evacuation duration. Gathering comprehensive data from diverse regions while considering cultural and regional variations is necessary to understand how occupants' behavior is influenced. Thus, this study focuses on examining the behavior of Malaysian hotel staff during unannounced fire drill to gain insights into factors affecting their behavior during pre-evacuation stage, such as fire experience, fire alarm, drill participation, fire training, and awareness. The study categorizes the actions performed by the hotel staff into sequences and analyses them based on influencing factors. The findings indicate that instead of immediately evacuating in response to emergency notification, the hotel staff engage in various actions. Most staff members initially investigate or ignore the emergency, resulting in longer pre-evacuation times. Moreover, the results suggest that previous drill participation and high awareness levels contribute to shorter pre-evacuation times. Conversely, previous fire experience, fire training, and fire alarm familiarity have no effect on pre-evacuation time.

In fire safety engineering analysis of sprinkler-protected residential buildings, the maximum heat release rate is a key parameter requiring consideration. Several documents provide advice for estimating the heat release rate of a sprinkler-controlled fire, with a prevailing suggestion that it is fixed upon activation of the first sprinkler. When carrying out deterministic analysis, this requires the engineer to assume fixed fire parameters and consider that sprinklers limit fire growth. To explore these assumptions, the study uses three deterministic models to estimate a sprinkler-controlled maximum heat release rate for a representative apartment layout. The models include Alpert's correlation, a B-RISK zone model and a computational fluid dynamics model in the Fire Dynamics Simulator. These deterministic models are compared to a probabilistic model in B-RISK, where Monte Carlo simulations are used to generate a range of maximum heat release rates from distribution functions for fire and sprinkler properties. An output distribution function is generated with a mean of 296.6 kW and a standard deviation of 503.8 kW, with a lognormal distribution (μ = 5.014, σ = 1.165) estimated as a best-fit. The deterministic models are estimated to sit in the 92–98 percentile range of this function, indicating that common deterministic assumptions are reasonably conservative. The article concludes with suggesting that, for deterministic analysis, a percentile between the 80th and 99th (340–2640 kW) could be qualitatively selected based on the design objectives, building situation and relative consequence of a fire. Further research is needed to establish guidelines for selecting appropriate percentiles across various building scenarios.

Polyethylene (PE) sandwich panels are being increasingly used in external building insulation, but they may also contribute to the upward spread of flames during fires. This work investigates the impact of core thickness and opening height on the combustion characteristics of PE sandwich panels. Small-scale experiments and numerical simulations show that flame stretching and intermittent flames occurr during combustion. The average flame spread height is proportional to the thickness and the opening height, and a dimensionless relationship between the flame height and the characteristic length is established. As the thickness increases, the high-temperature zone within the PE sandwich panels increases. The average mass loss rate is proportional to the thickness and opposite to the opening height. The findings of this study hold crucial theoretical significance for ensuring the safe design of windows and PE sandwich panels in high-rise buildings.

Pressure treated wood (PTW) and wood–plastic composites such as Trex® are popular materials for the construction of decks and other auxiliary structures, which are known to significantly contribute to spread of wildland fires into communities. In this work, representative samples of these materials were studied to determine their pyrolysis and combustion properties to enable simulation of fire growth on the surface of these building products. The pyrolysis property development process followed a well-established hierarchical approach where thermogravimetric analysis, differential scanning calorimetry, and microscale combustion calorimetry were used to parametrize kinetics and thermodynamics of the thermal decomposition and combustion, while controlled atmosphere pyrolysis and cone calorimetry tests performed on coupon-sized samples were used to parameterize thermal transport properties and validate performance of the fully parametrized pyrolysis models. PTW decomposition was captured using four sequential reactions with one additional reaction used to model vaporization of water. Trex® board was found to consist of two distinct layers: a thin outer layer and an internal core. The pyrolysis model for this material was constructed using some known properties of high-density polyethylene (PE) and the properties of PTW determined in this work. The outer layer was defined in the model to consist of PE and an inert additive, while the core was defined as a blend of PE and wood particles, which kinetics and thermodynamics of the thermal decomposition and combustion were successfully captured using the model developed for PTW.

This study investigates the combustion behavior, emissions, and aerosol production of four plant species: Laurus nobilis, Cistus monspeliensis, Photinia fraseri, and Cupressus sempervirens. The Heat Release Rate (HRR) and Smoke Production Rate (SPR) were measured, revealing that Cupressus sempervirens had the highest HRR and longest flame duration due to its higher bulk density. Emission Factors (EFs) for key compounds such as CO₂, CO, NO, and aerosols showed significant variation by species. Aerosol analysis indicated that the combustion of all plants primarily emitted fine particles, with the majority being ultrafine particles (PM_0.1), particularly in the 25–130-nm range. Particle size distributions were bimodal in number but monomodal in volume. These findings highlight the impact of plant characteristics on fire behavior and emissions, with significant implications for understanding fire dynamics in wildland–urban interfaces.

Using recycled concrete aggregates (RCA) in concrete has emerged as a promising solution to produce concrete with reduced environmental impact and adequate performance. However, a deeper understanding of the thermal and mechanical behavior of concrete made with RCA is still needed for further application in real structures. The present paper addresses one of the crucial issues for structural concrete: its behavior after exposure to high temperature. Four concrete mixes are studied: a reference concrete made with natural aggregates (NA), two concretes including 40% and 100% of coarse RCA as a direct replacement (DR) for coarse NA, and a concrete made with 100% of coarse RCA relying on a strength-based replacement (SBR). The SBR concrete mix was designed to achieve the same performance (28 days compressive strength and slump) as the reference concrete. All specimens were exposed to temperatures of 200, 400, and 600°C. After cooling, samples were evaluated for residual mass loss, thermal, and mechanical properties. Microstructural quantitative analyses were conducted over several square millimeters to show that interfaces between the old and new cement pastes, peculiar to concrete made with RCA, do not further promote fracture development. The results show that after exposure to high temperatures, the thermal and mechanical performances of concrete made with RCA are reduced in the same manner and extent as in concrete made with NA. When the RCA-based concrete is designed to achieve similar performance as concrete with NA at room temperature (SBR), the residual thermomechanical behavior is similar between both concretes.