Fire Safety Research Articles

Lignin-derived core-shell flame retardants for fire-safety rigid polyurethane (RPU) insulations

How to ensure the fire safety of rigid polyurethane (RPU) insulation materials remains a challenge. Herein, alkali lignin (AL) and 4,4'-diphenylmethane diisocyanate (MDI) were used as raw materials to construct bio-based cross-linked polyurethane structures on the surface of ammonium polyphosphate (APP) to obtain APP@AL flame retardants. APP@AL was combined with expandable graphite (EG) in varying proportions and applied to rigid polyurethane (RPU) foam to modify its flame retardancy and physico-mechanical characteristics. Compared with untreated RPU, the high interfacial compatibility increased the compressive strength of the flame-retardant RPUs by 10.8%, and the thermal insulation coefficient reached 22.8mW·m−1·K−1. The addition of flame retardant for each flame-retardant RPU was 30wt% of the polymethylene polyphenyl isocyanate. Owing to the P/C/O hybridized char layer in the combustion residues and the capture of gas by EG after expansion, APP@AL/EG not only reached the limiting oxygen index (LOI) of 27.1% but reduced the mean heat release rate and smoke release rate by 70.3% and 58.9%, respectively. This work presented a novel approach to designing environmentally friendly flame retardants for RPU foams with enhanced fire safety and superior overall performance. Additionally, it offers a novel strategy for the high-value conversion of lignin.

Enhanced flame retardancy and mechanical properties of poly (lactic acid) composites via piperazine pyrophosphate and nanoscale cerium dioxide synergistic flame retarding and uniaxial pre-stretching

The simultaneous improvement of flame retardancy and mechanical properties (including strength, rigidity, and toughness) of PLA was achieved for the first time. A synergistic flame retardant system including PAPP and nano-CeO2 was used to enhance the flame retardant properties of PLA. Especially, uniaxial pre-stretching was further used to improve the mechanical properties of the flame-retardant PLA composites. With the addition of just 1 wt% nano-CeO2, the flame retardant properties of PLA composite were significantly enhanced. Relative to pure PLA, the limiting oxygen index (LOI) of PLA/14 wt%PAPP/1 wt% nano-CeO2 increased from 20.2 % to 28.8 %, achieving a V-0 rating in the UL-94 test. Moreover, the peak heat release rate (PHRR) was reduced from 461KW/m2 to 230KW/m2. Notably, the flame-retardant PLA composites with excellent mechanical properties were achieved using uniaxial pre-stretching for the first time. After pre-stretching, the tensile strength, elongation at break and impact strength of the flame-retardant PLA were significantly increased to 79.82 MPa, 103.8 %, and 9.7 kJ/m2, respectively. This work proposes an ingenious strategy for significantly enhancing both the fire safety and mechanical properties of PLA composites.

Failure criterion and damage evolution of high-strength geopolymer concrete under compression-shear composite loading after high temperatures

Geopolymer concrete (GPC) holds significant potential for building fire safety design due to its green, low-carbon, and high-temperature resistant properties. In practical applications, concrete structures often face multiaxial composite loads. Therefore, investigating the composite stress performance of high-strength geopolymer concrete (HGPC) after exposure to high temperatures is crucial for assessing structural damage and enhancing fire prevention measures. This paper examines the compressive shear performance of HGPC at various temperatures T (20°C, 200°C, 400°C, 600°C) and stress ratios k (0.15, 0.3, 0.45, 0.6). The study analyzes failure patterns, shear load-displacement curves, shear strengths and their components, and peak shear deformation. Failure criteria are proposed to describe the damage patterns of HGPC under compressive shear loading after high temperatures. Additionally, the damage evolution process is evaluated using the energy method. The results show that HGPC damage surfaces penetrate the coarse aggregate at room temperature under compression-shear composite loading but shift to the aggregate-mortar interface at 600°C. Shear stiffness, peak shear strength, and residual strength increase with higher stress ratios but decrease with rising temperatures. Temperature affects peak shear strength by over 95 %, significantly more than the stress ratio. The shear strength decreases more slowly than compressive strength up to 400°C but more rapidly beyond 400°C. The cohesive strength of HGPC decreases with increasing stress ratio under different temperatures, while contact friction strength exceeds 50 % of peak shear strength. Shear dilation strength generally increases, then decreases, peaking at k = 0.45. The failure criterion based on the modified twin shear unified strength theory aligns best with experimental results. Furthermore, an increased stress ratio retarded the development of damage evolution, which was first accelerated and then slowed with rising temperature.

Interfacial engineering of 0D–2D hierarchical MXene@PEI@AgNC nanohybrids to achieve flame retardant, mechanical and antibacterial properties of ABS nanocomposites

It is an intractable challenge that the hierarchical MXene-based nanohybrid fillers are intended to modify the inherent flammability and easily breeding bacteria property of ABS polymeric materials, thereby facilitating wide applicability of ABS composites. Here, an interface engineering strategy was proposed, wherein polyethyleneimine (PEI)-modified silver nanocubes (AgNCs) was firmly assembled on MXenes via electrostatic interaction to construct 0D–2D hierarchical MXene-based nanohybrids (MXene@PEI@AgNC). The MXene was protected and the interface compatibility between MXene-based nanohybrid and ABS matrix was enhanced. Results revealed that the unique hierarchical structure of the composite promoted enhanced dispersion of MXene@PEI@AgNC in the ABS matrix. Combustion tests showed that 1.0 wt%MXene@PEI@AgNC provided the ABS with effective fire safety. Moreover, ABS-1.0 wt%MXene@PEI@AgNC exhibited a 31.88 % decrease in peak heat release rate, a 39.60 % decrease in peak smoke release rate, a 41.50 % decrease in peak CO2 production rate, and a 50.04 % reduction in the smoke factor. Meanwhile, 1.0 wt%MXene@PEI@AgNC improved the tensile strength of ABS-1.0 %MXene@PEI@AgNC (+18.1 %) without reducing the elongation at break. They also enhanced the antibacterial properties of ABS-1.0 %MXene@PEI@AgNC. This study proposed a novel and feasible approach to address the interfacial stability of MXene and to construct MXene-based hierarchical nanoblends, thereby facilitating the wide practical applications of polymeric nanomaterials in industry.

Flame spread characteristics of densified wood with various sample widths and densities

Densified wood (DW) is a novel functional material with great mechanical properties, its structural characteristics make it attractive as an ideal building material for mid-to-high-rise timber constructions. However, its flame spread characteristics is not yet fully understood, which threatens its further developments and applications. This study experimentally and analytically investigates the impact of density and width on the flame spread behaviors and heat transfer characteristics of DW. Flame spread rate, mass loss rate (MLR), and flame height decrease with increasing wood density. Both MLR and flame height increase with the increasing width, while flame spread rate increases first and then decreases. Dimensionless power-law relationships among them were established, which well predict the measurements. The dominant gaseous heat transfer transits from radiation to convection with the increase of density. The critical density for this transition is increased with width. Both width and density impact the preheating length and total heat flux, which are combined to influence the flame spread rate. A dimensionless correlation among them was established with an R2 of 0.915 to the experiments of current and previous publications. This work helps to understand flame spread of DW and benefits the fire safety in timber construction.

Caramel doped with aromatic compounds as halogen- and phosphorus-free flame-retardant strategy for wool fabric

The development of halogen- and phosphorus-free flame-retardant strategies is urgently needed in textile industry. In this study, a caramel product doped with aromatic compounds was developed via caramelization and aldol reactions using glucose and p-phthaldialdehyde. The modified caramel (Car@PDA) was subsequently used as a sustainable approach to improve flame retardancy of wool fabric. The flame retardancy, washing durability, heat generation, and flame-retardant mode of action of Car@PDA on wool fabric were investigated. The modified wool fabrics showed excellent flame retardancy, with the limiting oxygen index increasing to 32.5 % and the damaged length decreasing to 10.1 cm, with good self-extinguishing capacity. Car@PDA could combine with wool fibers through Schiff base reaction and electrostatic attraction, so the modified wool fabrics still self-extinguished and met the B1 flame-retardant requirements after 10 washing cycles. The modified wool showed significantly decreased heat release capacity and fire growth rate, suggesting high fire safety. Car@PDA promoted the decomposition of the fabric to form char barrier, thereby achieving an effective flame-retardant effect. In addition, the Car@PDA modification had a minimal effect on the tensile strength and handle of wool fabric. This study provides an innovative way to create bio-based, halogen- and phosphorus-free flame-retardants for protein wool fabrics.

Suggestions on Grassroots Fire Safety Management for Smart City Construction

In this context, China has proposed "adhering to the overall concept of national security" and "adhering to the positive interaction between high-quality development and high-level security" to ensure the safety of life and property of the people in their pursuit of a better life. In the field of safety in China, fire safety has always been the top priority, and its impact has been widely reflected in the social, scientific and technological and economic fields, but there are still large shortcomings in the grass-roots fire safety management in China, so it is particularly important to find a suitable management approach. Based on this, this paper synthesizes the views of various scholars, summarizes and analyzes the exploration of grass-roots fire safety governance and the existing problems, and finds the appropriate governance approach, in order to provide a certain reference for China's grass-roots fire safety governance

Levels of Effectiveness of Water Curtain Equipment Applied When Mitigating Fire Compartment Installation of Logistics Facilities

Mock-up tests and fire simulations were performed to verify the effectiveness of water curtain equipment in mitigating fire compartment installation of logistics facilities. The radiant-heat-blocking effect of the water curtain equipment differed significantly based on the type of drencher head, and a blocking effect was observed. Additionally, the radiant temperature and heat flux were significantly reduced when the installation intervals of the drencher heads of the water curtain equipment were reduced. Therefore, improving the standards related to the water curtain equipment of logistics facilities, e.g., providing drencher head specifications, restricting the sizes of the openings, and narrowing the installation intervals of the drencher heads, is necessary to ensure the fire safety of water curtain equipment.

Improvement of Safety Standards for Railway Station Platforms

This study compares and analyzes the fire safety standards of both domestic and international railway station platforms by investigating the installation status of fire protection facilities in platforms with a total floor area of over 5,000 m<sup>2</sup> in the Chungcheong region. The existing fire protection facilities require improvement in their standards by taking into account various factors, such as the location of railway stations, openness of platforms, and amount of combustible materials. The installation standards for fire protection facilities on platforms must be clearly defined and reinforced. Additionally, the installation of evacuation elevators is required for wheelchair users on underground station platforms without any open areas, as this would facilitate easy evacuation in the event of a fire.

Beyond the Ire of Flames: Work Experiences of Bureau of Fire Protection (BFP) Station Chiefs

Fire occurrences have significantly risen in recent years. These fires endanger lives, cause economic damage, and harm the environment. Uncontrolled fires are a major reason for building collapses and injuries. Building fires cause trauma due to the loss of belongings and the building itself. Existing fire safety systems are failing due to unaddressed factors causing building fires (Rathnayake et al., 2020). This study explored the experiences of the station chiefs of the Bureau of Fire Protection in Iloilo Province, Philippines, through a qualitative research method. The participants of this study were the selected ten (10) BFP station chiefs. All participants were subjected to an individual in-depth interview. The findings of this study are described in emergent themes. Six (6) emergent themes described the positive and negative experiences of the informants in the performance of their duties. For the positive experiences, two (2) emergent themes were developed, namely Personal Satisfaction Through Job Fulfillment and Workplace Camaraderie and Support. For the negative experiences, four (4) emergent themes were also developed, namely: Inadequate Resources and Financial Challenges, Complexity of Leadership and Personnel Management, Bombarded with Public Dissatisfaction, and Operational Delays and Equipment Failures. Meanwhile, three (3) emergent themes were formulated to explain how the participants address the challenges encountered in the performance of their duties, namely: Empowering Collaboration and Support Networks, Bolstering Preventive Measures and Education, and Embodying Resilience and Adaptability. Finally, three (3) emergent themes were created to express the aspirations of participants to improve the quality of their services, namely Continuous Training and Professional Development, Adequate Fiscal Allocation and Service Facilities, and Improvement of Personnel and Staffing Issues. Based on the emergent themes identified, it is recommended that the fire station chiefs be enhanced by providing them with specialized training and career development programs. This can be accomplished by the successful integration of the latest firefighting technologies in the specialized training to enhance the response effectiveness of their station.

Defining a maximum heat release rate probability distribution function for design fires in sprinkler‐protected residential buildings

AbstractIn 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.

Optimizing Ammonium Polyphosphate–Acrylic Intumescent Coatings with Sustainable Fillers for Naval Fire Safety

This study explores the potential of natural and recycled materials to enhance the fire behavior of eco-friendly intumescent coatings, compared to a traditional ammonium polyphosphate (APP)-based one. To achieve this, cork, halloysite clay, and recycled glass were evaluated as natural fillers and sustainable components within the coating formulation. The aim was to reduce the reliance on synthetic materials and minimize the environmental impact while maintaining fire performance. Fire exposure tests were conducted to assess the in situ char formation and its relationship to the heat source and char foaming process. The results highlighted that all functionalized coatings exhibited suitable intumescent behavior. The best results were evidenced by cork-filled coating that evidenced an intumescent capacity about 40% higher than the traditional ammonium polyphosphate (APP)-based one. This provided valuable insights into the coating’s real-time response to fire, determining its suitability for various fire-resistant applications.

Influence of Wind Direction on Fire Spread on High-Rise Building Facades

In order to study the influence of wind direction on fire spread on building facades, a three-dimensional model of a high-rise building was built with PyroSim software. Numerical simulations were conducted with five wind directions (0°, 45°, 90°, 135° and 180°) and a reference wind speed of 3 m/s. The results show that the fire spread on the building facade was most significant on the leeward side, followed by the upwind condition. The horizontal spread of fire was promoted by crosswinds at 45°, 90° and 135°, while its vertical spread was inhibited. Among these, the inhibitory effect of the 45° crosswind was the greatest. The fire spread area under the leeward condition was the greatest at approximately 341.3 m2, accounting for 17.1% of the facade, and the vertical spread velocity under the condition of no wind was the fastest at 0.075 m/s. In this study, the motion characteristics of facade fire spread under different wind directions were determined, providing supporting evidence to enhance fire safety prevention and control measures in high-rise buildings.

On the Mathematical Modeling of a Fire Thermogasodynamic Pattern and Using a Priory Calculation of Fire Hazard Factors in Forensic Fire Examination

The article presents the disadvantages of the “risk analysis” methodology for fire safety assessment of buildings and its inadmissibility in forensic practice. The option of numerical modeling application for fire hazards evaluation in forensic fire-examination is analyzed.

ИССЛЕДОВАНИЕ ВОЗНИКНОВЕНИЯ ПОЖАРА ОТ ВОСПЛАМЕНЕНИЯ И ВЗРЫВА ПАРОВОЗДУШНОЙ СМЕСИ ПРИ ПРОВЕДЕНИИ ГАЗОСВАРОЧНЫХ РАБОТ

Using the example of a real fire that occurred as a result of violations of fire safety requirements during gas welding operations, it is demonstrated how the combined use of instrumental and computational methods makes it possible to determine the cause of the fire. The nature of combustible substances has been determined by fluorescence spectroscopy, gas-liquid chromatography and infrared spectroscopy. Using mathematical calculations, the amount of combustible substances necessary for the formation of an explosive mixture was determined. It is demonstrated how a combination of physical-chemical research methods and computational methods, allows for the determining the causal relationship between gas welding operations and the aforementioned explosion.

Quantitative Study of Thermal Response of Timber–Concrete Composite Structures Under Traveling Fire Using Energy Equivalence Method

ABSTRACTThe time equivalent method can be used to quantify the fire intensity of a traveling fire into the time of action of the standard fire, which in turn can be used to assess the extent of damage to a structure under a traveling fire. However, an effective time equivalence method for timber structures has not been developed yet. Therefore, this paper proposed an energy‐based time equivalent method, referred to as the “energy equivalence method (EEM)”, for evaluating the fire resistance of timber structures under traveling fire, and validates its effectiveness through a series of fire tests. The results demonstrate that the EEM effectively quantifies the fire intensity endured by glulam under traveling fire as the equivalent exposure time under the standard fire. Furthermore, the EEM was utilized to investigate the damage behavior of a single‐layer Timber‐Concrete Composite (TCC) frame under traveling fire. The results reveal variations in the fire intensity experienced by the structure at different locations under the same traveling fire scenario, with the most severe damage occurring at a position 40% relative to the ignition end. The fire scale determines the non‐uniformity of the fire intensity and the extent of structural damage, as smaller‐scale fires (fire sizes between 10% and 40%) not only result in significant variations in damage levels at different locations but also have a more adverse impact on the structure. In fire safety design, the selection of standard and traveling fire design methods should be based on the fire scale.

მიწისქვეშა ავტოსადგომების კვამლისაგან დაცვა ხანძრის დროს

The work examines current issues of fire, sanitary, hygienic and environmental safety of ventilation of underground parking lots. It has been established that, according to European standards, smoke removal systems with jet fans act much more efficiently than air ducts, quickly displacing smoke and exhaust gases towards the air intake grilles, from where and they come out. The design and parameters of the ventilation system are selected based on its ability to quickly and safely ensure the evacuation of people through smoke-free exits, as well as provide air parameters in the parking lot that meet the requirements of the design and installation of a ventilation unit in accordance with industry regulations of Georgia.

Sustainable lignin-based high-efficiency flame-retardant epoxy resins with excellent mechanical properties

As an abundant natural aromatic polymer, how to realize the high-value utilization of lignin (LA) is still a difficult problem. Herein, a sustainable flame retardant (LA@APP) was synthesized through hydrogen bonding interactions between LA and ammonium polyphosphate (APP), then flame retarded alone epoxy resin (EP/LA@APP). With loading of 6 wt% LA@APP, the LOI of EP/LA@APP6 rose to 27.9 % and achieved UL-94 V0 rating. Meanwhile, EP/LA@APP6 presented a 63.5 % reduction in peak of heat release rate (pHRR) and an 51.3 % decrease in peak of smoke production rate (pSPR). LA@APP could promote the EP composites to form the denser and more continuous expanded charring residuals than APP during the combustion process, effectively shielding the underlying epoxy substrate and thus enhancing fire safety. Additionally, the shell layer of LA@APP, abundant in hydroxyl groups and methoxy groups, effectively improved the compatibility and interfacial interaction with EP. Therefore, the tensile, flexural and impact strength of EP/LA@APP6 reached 50.8 MPa, 86.1 MPa and 7.81 kJ/m2, higher than those of pure EP at 48.3 MPa, 81.5 MPa and 7.45 kJ/m2. This flame retardant with simultaneously enhanced fire safety and mechanical properties of epoxy resin was expected to realize the high-level utilization of lignin.

Understanding human-obstacle interaction dynamics on staircases: Implications for emergency evacuation and fire safety in high-rise buildings

Interactions between system components, including human-obstacle, human-building, human-robot, and human-human, significantly impact public safety, system efficiency, and functionality. A deeper understanding of these systems is essential to enhance their resilience and effectiveness. Despite the significance of these interactions, empirical research is limited, particularly regarding behavioral mechanisms when interacting with obstacles on stairways. Our study examines the evacuation behavior of 90 evacuees on the staircase of a high-rise building under different temporary obstacle conditions to understand how key factors affect decision-making and motion behavior during stairway descent. The experiments considered obstacle shapes as control variables and analyzed evacuation time, inner and outer stair route choices, regional speed fluctuations, velocity-relative displacement, evacuation efficiency, and biomechanical analysis of occupants’ comfort. Results show that larger obstacle shapes, increased evacuation urgency time, and closer proximity to the wall lead to a higher proportion of the splitting to merging state before and after obstacle interaction. A strong inner stair route preference emerges in no-obstacle conditions, with significant mean speed differences in downward movements when encountering temporary obstacle. Three phases of average speed variations are observed: deceleration, acceleration, and continued deceleration for the outer route; and deceleration followed by uniform speed for the inner route. A method was developed to calculate regional speed fluctuation using average speeds from trajectories. Comfort analysis revealed that temporary obstacle on building stairways significantly impact safe evacuation. Overall, these findings enhance the understanding of crowd dynamics in high-rise building emergency evacuations, with implications for model development, architectural design, building operations, emergency preparedness, behavioral cognition, and fire safety.

CFD-based analysis of deviations between thermocouple measurements and local gas temperatures during the cooling phase of compartment fires

Data from thermocouple (TC) measurements play a pivotal role in fire safety science and engineering studies. It is well-known that there are deviations from the actual local gas temperature and many studies have led to the development of correction factors. The present study focuses on these deviations inside compartments through a systematic series of CFD simulations, performed with Fire Dynamics Simulator (FDS), version 6.8.0. A canonical cubic box is used as geometry. This allows for the demonstration of the impact of the presence of smoke, with variable optical thickness, on the TC data as retrieved from FDS. Significant differences are observed between TC measurements and local gas temperatures. Corrections as developed for TC measurements in open atmospheres cannot be readily applied in compartment configurations, where smoke properties change both spatially and temporally.