Fire and Materials最新文献

The wildland-urban interface (WUI) fire problem continues to perplex governments around the world. The WUI fire situation is not becoming better across the earth and globally harmonized test standards are required to help lessen the destruction in the event of WUI fire disasters. In this brief overview, a review of activities undertaken in ISO TC92/WG14, the Large Outdoor Fires and the Built Environment Working Group, under ISO TC92, is provided. Specifically, the genesis of how this working group came to be formed is provided as well as an overview of current documents that have been published by ISO TC92 and developed by ISO TC92/WG14. The review closes with recently added new work items in ISO TC92/WG14 and some possible future challenges.

With a drive for sustainable construction, various products are being introduced to promote recycling, but often their properties relation to behaviour in fire are not known. In this paper, the fire performance of crumb rubber and a plastic eco-aggregate, called RESIN8, were assessed. Various tests, including cone calorimeter, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC), were conducted. These are supplemented by numerical calculations and the Coats–Redfern kinetic model to quantify the thermal and fire properties of these materials. Cone calorimeter tests were conducted at 35 and 50 kW m⁻², while the critical heat flux (CHF) values were determined using a range of irradiance levels. Time to ignition (TTI), heat release rate (HRR), peak heat release rate (pHRR), and thermal fire hazard parameters were quantified. Both materials were classified under the high thermal fire hazard class. The peak thermal decomposition rates occurred at 365°C (single peak) for CR and at 435°C and 550°C (two peaks) for RESIN8. The calculated activation energy values were 66.7 kJ mol⁻¹ for crumb rubber and 55.1 and 43.9 kJ mol⁻¹ for RESIN8 in the first and second stages, respectively. These eco-aggregates could pose a significant thermal fire hazard, in the recycling facility during and after the recycling process, as well as when stored in bulk and when incorporated in large quantities in construction systems. Further investigation is crucial for understanding the effect of incorporating these eco-aggregates within masonry and concrete systems from a fire safety perspective.

In this paper, we investigate the plug-holing phenomenon under the influence of natural smoke venting in deeply buried tunnel shafts using a fire dynamics simulator based on a large eddy simulation model. Additionally, we discuss the effects of heat release rate and shaft height. The results indicate that the temperature distribution of the smoke upstream of the fire remains consistent when the height of the shaft does not exceed 20 m. Once the shaft height reaches 50 m, the temperature of the smoke upstream of the fire decreases with the increase in shaft height. Simultaneously, the smoke downstream of the fire can be completely discharged through the shaft. As the shaft height increases in the deeply buried tunnel, the degree of plug-holing increases, leading to reduced smoke evacuation efficiency. This phenomenon is caused by the horizontal inertia force and vertical thermal buoyancy of the smoke below the shaft. The critical plugging phenomenon occurs when Ri = 2.72, as determined through force analysis of the smoke. Subsequently, we analyze the mechanism by which shaft height and heat release rate influence plug hole height and establish a quantitative expression equation for plug-holing height.

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.