Assessing the reaction to fire of cables by a new bench‐scale method

The recently approved EU Construction Products Regulation (CPR) applies to cables as construction products. The difficulty of predicting the fire performance of cables with respect to propagation of flame and contribution to fire hazards is well known. The new standard EN 50399 describes a full‐scale test method for the classification of vertically mounted bunched cables according to CPR. Consideration of the material, time, and thus cost requires an alternative bench‐scale fire test, which finds strong demand for screening and development purposes. The development of such a bench‐scale fire test to assess the fire performance of multiple vertically mounted cables is described. A practical module for the cone calorimeter is proposed, simulating the fire scenario of the EN 50399 on the bench scale. The efficacy of this module in predicting full‐scale CPR test results is shown for a set of 20 different optical cables. Key properties such as peak heat release rate (PHRR), fire growth rate (FIGRA), and flame spread are linked to each other by factors of around 5. In a case study, the bench‐scale test designed was used to investigate the influence of the main components on the fire behaviour of a complex optical cable. Copyright © 2016 John Wiley & Sons, Ltd.     

An adhesion test method for spray‐applied fire‐resistive materials

Adhesion of spray‐applied fire‐resistive materials (SFRMs) to steel structures is critical in enabling a building to remain functional during a fire for a specific period of time for life safety and fire department access. Empirical tests such as ASTM E736 have been widely adopted by the industry in an effort to ensure sufficient bonding between SFRMs and steel structures. ASTM E736 assesses the adhesion of SFRMs by using tensile strength, a failure parameter that depends on the test geometry and has limited use for predicting failure in other geometries and conditions. These limitations have produced an urgent need for a scientifically based adhesion test method. In this paper, we propose a new test method that would provide more fundamental information that is independent of test geometry and has predictive capability. This paper utilizes a fracture energy‐based failure criterion (G_C) to characterize the adhesion between SFRMs and steel. The theoretical basis of this test method is validated by experimental compliance tests. The dependence of G_C on various test variables such as specimen width, substrate type, SFRM formulation, and test rate are examined. A comparison between this new test method, and the current widely used strength‐based test method is also presented. Copyright © 2010 John Wiley & Sons, Ltd.     

Enhancement of fire retardancy properties of glass fibre–reinforced polyesters composites

This paper presents the results of an experimental investigation on the fire retardancy properties of glass fibre–reinforced polyester (GFRP) composites with bisphenol‐A vinylester and isophthalic polyester as matrices and low electrical conductivity E‐glass fibres as reinforcement. The fire protection systems tested were alumina trihydrate (ATH), decabromodiphenyl ether (DBDE), and antimony trioxide (Sb₂O₃). A mass loss cone calorimeter was used to obtain the properties of heat release rate (HRR), peak HRR, total heat released, total mass loss, time to ignition, and time of combustion. Moreover, limiting oxygen index (LOI), UL‐94, and glow‐wire tests were also performed. The fire tests were carried out in order to investigate if the combination of ATH and DBDE could have “additive,” “antagonistic,” or “synergistic” effects on the flame retardant properties of the GFRP studied in this work. In addition, the influence of the ATH content variation on flame retardant properties was also evaluated. The results indicate that the sole addition of ATH at 47.7 phr could lead to the complete inhibition of the composites ignition, while the materials containing DBDE exhibit ignition and flame propagation in the cone calorimeter test.     

Comparison of simulated wet bench fires with small‐ and intermediate‐scale fire tests

Fire hazard studies of clean room facilities indicated that significant losses due to fire may occur in the semiconductor industry. The present study reports the results of full‐scale wet bench fire tests conducted (1) to assess the fire hazards of existing wet bench materials not meeting the listing requirement of NFPA 318, (2) to assess the impact on wet bench fires of engineered materials with improved flammability characteristics, and (3) to compare the observed fire behavior with the results of simpler small‐ and intermediate‐scale fire tests using the same materials. The full‐scale wet bench fires were observed to be consistent in terms of chemical heat release rate, fire propagation, and smoke generation with the results of the small‐ and intermediate‐scale test results. The simpler fire tests are incorporated in FM Approvals 4910 certification for materials to be used in semiconductor fabrication facilities. The small‐scale test protocol is also standardized in NFPA 287. Copyright © 2008 John Wiley & Sons, Ltd.     

Effectiveness of pre‐applied wetting agents in prevention of wildland urban interface fires

The purpose of the work described in this paper is to investigate the effectiveness of pre‐wetting structures, dead fuels, and landscaping plants in preventing fire spread from wildland fires to structures. Critical fluxes for fire growth were determined using intermediate‐scale testing for three wetting agents (water, type A foam, and gel) applied to 10 landscaping plants conditioned to 20% moisture, a mulch material, and four external structural materials (vinyl siding, plywood siding, asphalt shingle roofing, and cedar shake roofing). The critical flux for fire growth values was determined at 3‐min heat radiation exposure and simultaneous 300‐mm long flame exposure. Test specimens were exposed to various durations and intensities of drying prior to exposing them to heat radiation. Application of water or foam provided no noticeable protection. Gel was effective in providing protection even after 60 min of laboratory condition drying but was less successful when exposed to fire weather simulating accelerated drying. Some uncertainty is associated with the results of this work because of the variability of landscaping plants and gel wetting agent application uniformity. The intermediate‐scale test results were verified using full‐scale testing. Copyright © 2012 John Wiley & Sons, Ltd.     

Highly Efficient Quencher‐Free Molecular Beacon Systems Containing 2‐Ethynyldibenzofuran‐ and 2‐Ethynyldibenzothiophene‐Labeled 2′‐Deoxyuridine Units

We have prepared two fluorescent DNA probes—U^DBF and U^DBT, containing 2‐ethynyldibenzofuran and 2‐ethynyldibenzothiophene moieties, respectively, covalently attached to the base dU—and incorporated them in the central positions of oligodeoxynucleotides (ODNs) so as to develop new types of quencher‐free linear beacon probes and investigate the effect of functionalization of the fluorene scaffold on the photophysical properties of the fluorescent ODNs. The ODNs containing adenine flanking bases (FBs) displayed a selective fluorescence “turn‐off” response to mismatched targets with guanine bases; this suggests that these probes could be used as base‐discriminating fluorescent nucleotides. On the other hand, we observed a “turn‐on” response to matched targets when the U^DBF and U^DBT units of ODNs containing pyrimidine‐based FBs were positioned opposite the four natural nucleobases. In particular, an ODN incorporating U^DBT and cytosine FBs has potential use in single‐nucleotide polymorphism typing.     

Fire performance of closed‐cell charring insulation materials in plasterboard‐insulation assemblies

This paper presents an experimental study on the fire performance of two types of plastic charring insulation materials when covered by a plasterboard lining. The specific insulation materials correspond to rigid closed‐cell plastic foams, a type of polyisocyanurate (foam A) and a type of phenolic foam (foam B), whose thermal decomposition and flammability were characterised in previous studies. The assemblies were instrumented with thermocouples. The plasterboard facing was subjected to constant levels of irradiation of 15, 25, and 65 kW m^?2 using the heat‐transfer rate inducing system. These experiments serve as (1) an assessment of the fire behaviour of these materials studied at the assembly scale and (2) an identification of the fire hazards that these systems pose in building construction. The manifestation of the hazards occurred via initial pyrolysis reactions and release of volatiles followed by various complex behaviours including char oxidation (smouldering), cracking, and expansion of the foam. Gas‐phase conditions may support ignition of the volatiles, sustained burning, and ultimately spread of the flame through the unexposed insulation face. The results presented herein are used to validate the insulation “critical temperature” concept used for a performance‐based methodology focused on the selection of suitable thermal barriers for flammable insulation.     

Apparatus for the vertical orientation cone calorimeter testing of flexible polyurethane foams

Of concern to regulators and fire safety engineers is how flexible polyurethane foam drips and flows during burning. Specifically, flexible polyurethane foam forms a burning ‘pool’ of liquid as the foam decomposes, which can lead to accelerated flashover events. To fully study this phenomenon where the ‘pool fire’ accelerates heat release, large‐scale tests like the furniture calorimeter (American Society of Testing and Materials (ASTM) E1537) are used, and no small‐scale technique exists. In this paper, we present our work in developing a new sample holder that works with a bench‐scale heat release test, the cone calorimeter (ASTM E1354). The holder was built upon designs developed by the National Institute of Standards and Technology, which placed the foam in a cage in a vertical orientation during cone calorimeter testing. In this paper, we show the schematics for this test apparatus, as well as results obtained with this apparatus on four different flexible foams (shape memory and high‐density foam, flame retarded and non‐flame retarded). We compare the results from the vertical testing with that obtained via traditional horizontal ASTM E1354 testing. The advantages and disadvantages of this new apparatus are discussed in this paper. Copyright © 2014 John Wiley & Sons, Ltd.     

Effects of variations in incident heat flux when using cone calorimeter test data for prediction of full‐scale heat release rates of polyurethane foam

The development of methods to predict full‐scale fire behaviour using small‐scale test data is of great interest to the fire community. This study evaluated the ability of one model, originally developed during the European Combustion Behaviour of Upholstered Furniture (CBUF) project, to predict heat release rates. Polyurethane foam specimens were tested in the furniture calorimeter using both centre and edge ignition locations. Input data were obtained using cone calorimeter tests and infrared video‐based flame area measurements. Two particular issues were investigated: how variations in incident heat flux in cone calorimeter tests impact heat release rate predictions, and the ability of the model to predict results for different foam thicknesses. Heat release rate predictions showed good agreement with experimental results, particularly during the growth phase of the fire. The model was more successful in predicting results for edge ignition tests than for centre ignition tests and in predicting results for thinner foams. Results indicated that because of sensitivity of the burning behaviour to foam specimen geometry and ignition location, a single incident heat flux could not be specified for generating input for the CBUF model. Potential methods to determine appropriate cone calorimeter input for various geometries and ignition locations are discussed. Copyright © 2014 John Wiley & Sons, Ltd.     

Comparison of flammability measurements in vertical and horizontal exhaust duct in the ASTM E‐2058 fire propagation apparatus

The ASTM E‐2058 fire propagation apparatus (FPA) is capable of measuring time to ignition, chemical and convective heat release rates, mass loss rate, smoke generation rate, generation rates of CO, CO₂ and O₂ consumption rate, effective (chemical) heat of combustion and vertical fire propagation of materials. The original design of the FPA incorporated a vertical exhaust system with the measurement section finishing about 3.5 m from the floor. The exhaust measuring duct of the new FPA is horizontally oriented to enable its use in a wider range of laboratory environments. In this paper, the functionality of the new FPA was compared with the original FPA. The measurements and results indicate that the performance of the new FPA is equivalent to the original FPA. Copyright © 2003 John Wiley & Sons, Ltd.     

The calculation of the heat release rate by oxygen consumption in a controlled‐atmosphere cone calorimeter

The standard cone calorimeter according to ASTM E 1354 and ISO 5660 enables reaction‐to‐fire tests to be performed in ambient atmospheric conditions. A controlled‐atmosphere chamber modifies the standard apparatus in a way that allows tests to be performed in nonambient conditions as well. The enclosed chamber is placed underneath the standard exhaust hood and does not have a closed connection to the hood. With this open arrangement, the exhaust gases are diluted by excess air drawn in from the laboratory surroundings. Heat‐induced changes in the consequential dilution ratio affect the calculation of fire quantities and, when neglected, lead to deviations of up to 30% in heat release rate. The paper introduces a test protocol and equations to calculate the heat release rate taking dilution effects into account. A mathematical correction is shown that compensates for the dilution effects while avoiding extensive mechanical changes in the equipment. Copyright © 2013 John Wiley & Sons, Ltd.     

Revealing the inner secrets of intumescence: Advanced standard time temperature oven (STT Mufu+)—μ‐computed tomography approach

Intumescent coatings have been used for fire protection of steel for decades, but there is still a need for improvement and adaptation. The key parameters of such coatings in a fire scenario are thermal insulation, foaming dynamics, and cohesion. The fire resistance tests, large furnaces applying the standard time temperature (STT) curve, demand coated full‐scale components or intermediate‐scale specimen. The STT Mufu⁺ (standard time temperature muffle furnace⁺) approach is presented. It is a recently developed bench‐scale testing method to analyze the performance of intumescent coatings. The STT Mufu⁺ provides vertical testing of specimens with reduced specimen size according to the STT curve. During the experiment, the foaming process is observed with a high‐temperature endoscope. Characteristics of this technique like reproducibility and resolution are presented and discussed. The STT Mufu⁺ test is highly efficient in comparison to common tests because of the reduced sample size. Its potential is extended to a superior research tool by combining it with advanced residue analysis (μ‐computed tomography and scanning electron microscopy) and mechanical testing. The benefits of this combination are demonstrated by a case study on 4 intumescent coatings. The evaluation of all collected data is used to create performance‐based rankings of the tested coatings.     

Waste‐derived low‐cost mycelium composite construction materials with improved fire safety

Mycelial growth attracts academic and commercial interest because of its ability to upcycle agricultural and industrial wastes into economical and environmentally sustainable composite materials using a natural, low‐energy manufacturing process able to sequester carbon. This study aims to characterise the effect of varying ratios of high silica agricultural and industrial wastes on the flammability of mycelium composites, relative to typical synthetic construction materials. The results reveal that mycelium composites are safer than the traditional construction materials considered, producing much lower average and peak heat release rates and longer time to flashover. They also release significantly less smoke and CO₂, although CO production fluctuated. Rice hulls yielded significant char and silica ash which improved fire performance, but composites containing glass fines exhibited the best fire performance because of their significantly higher silica concentrations and low combustible material content. Higher concentrations of glass fines increased volume‐specific cost but reduced mass‐specific and density‐specific costs. The findings of this study show that mycelium composites are a very economical alternative to highly flammable petroleum‐derived and natural gas‐derived synthetic polymers and engineered woods for applications including insulation, furniture, and panelling.     

The influence of carbon‐based fillers on the flammability of polypropylene‐based co‐extruded wood‐plastic composite

Comparative analysis of the effect of carbon‐based fillers with different particle sizes and morphologies on the flammable properties of a co‐extruded wood‐plastic composite is performed. Five carbon‐based fillers, namely carbon black, carbon nanotubes, graphite, expandable graphite, and carbon fibers were loaded into the shell layer of the composite. The flammability was characterized by using the cone calorimeter technique. The nanosized fillers, carbon black and carbon nanotubes, had a larger impact on the peak of the heat release rate, decreasing it by 16% and 17%, respectively. The samples with graphite, expandable graphite, and carbon fibers, decreased the peak of the heat release rate by 10%, 6%, and 11%, respectively. The total heat release decreased slightly for all the samples, except for the carbon fibers–wood‐plastic composite. The effective heat of combustion decreased also slightly, and carbon monoxide production increased for all the studied composites. Copyright © 2015 John Wiley & Sons, Ltd.     

Screening of plenum cables using a small‐scale fire test protocol

The extent of flame propagation of electric cables in the FM Global intermediate‐scale parallel panel test (PPT) using a 60 kW sand burner has been correlated with a dimensional fire propagation index (FPI,)[(m/s^1/2)/(kW/m)^2/3] derived from ignition and vertical propagation tests in small‐scale ASTM E‐2058 Fire Propagation Apparatus (FPA). Two distinct types of fire behavior were observed in the PPT. The cables that did not propagate beyond the vicinity of the ignition burner flames have a FPI equal to or less than 7 [(m/s^1/2)/(kW/m)^2/3], whereas cables that propagated to the top of the 4.9 m parallel panels had a FPI equal to or greater than 14 [(m/s^1/2)/(kW/m)^2/3]. All the plenum rated (Ul‐910 or NFPA 262 tested) cables tested in this study did not exhibit flame propagation in the PPT, had FPI values of 7 [(m/s^1/2)/(kW/m)^2/3] or less and generated considerably lower smoke than those cables that propagated in the PPT. Based on this study, it is suggested that FPI measured in ASTM E‐2058 FPA may be used for screening cables for UL‐910 or NFPA262 tests, thus requiring substantially less cable to be supplied for testing. Copyright © 2005 John Wiley & Sons, Ltd.     

The effect of fire‐retardant additives and a surface insulative fabric on fire performance and mechanical property retention of polyester composites

This study investigates the simultaneous use of conventional fire‐retardant additives and an insulative intumescent thermal barrier/mat to improve the fire performance and mechanical property retention of glass‐fibre‐reinforced polyester (GRP) composites. Significant reductions in the peak heat release rate (PHRR) and total heat release (THR) were observed from measured cone calorimetric data following the addition of nitrogen, phosphorous, halogen containing and hydroxylated fire‐retardant additives. Some fire‐retarded glass‐fibre‐reinforced composites further protected by an intumescent mat containing silicate fibres, expandable graphite and borosilicate glass bound together by an organic matrix show further reductions in PHRR. Despite improving the fire retardancy of the composites, the presence of fire‐retardant additives alone does not improve flexural modulus retention following exposure to a heat source. However, the introduction of a ‘passive’ fire proofing insulative fabric enhances fire performance while preserving the mechanical properties of composites exposed to high heat fluxes or fires. Copyright © 2010 John Wiley & Sons, Ltd.     

Experimental study of tenability during a full‐scale motorcoach tire fire

Full‐scale fire experiments were conducted at the National Institute of Standards and Technology (NIST) to investigate tire fire interactions with the passenger compartment of a motorcoach. A single full‐scale experiment with a partially furnished interior was conducted to investigate tire fire growth within the passenger compartment and the onset of untenable conditions. A tire fire was initiated using a burner designed to imitate the frictional heating of hub and wheel metal caused by failed axle bearings, locked brakes, or dragged blown tires. Measurements of interior and exterior temperatures, interior heat flux, heat release rate, toxic gases, and visibility were performed. Standard and infrared videos and still photographs were also recorded. The results of this single experiment showed that after fire penetration into the passenger compartment, the tenability limits were reached within 8 minutes near the fire and within 11 minutes throughout the passenger compartment.     

Fire properties of surrogate refuse‐derived fuels

This paper investigates the fundamental fire properties of surrogate refuse‐derived fuels (RDF), a class of multicomponent materials characterized by high void fraction, with particles of polydisperse sizes and significant internal porosity. A surrogate RDF was developed to improve the reproducibility of experimental measurements. This surrogate RDF reflects typical municipal solid waste collected in the city of Newcastle, in the state of New South Wales in Australia. The material consists of shredded newspaper, wood, grass and plastic bags, with small amounts of sugar and bread. About 95% of the material passes through 50 mm square screens, as required by ASTM E828 standard for RDF‐3 specification. The experiments presented in this paper were performed with the components of the RDF dried in a forced‐air oven at 103° C, except for grass which was dried under nitrogen. The material was found to be very hygroscopic, requiring special care in handling. The experiments performed in the cone calorimeter were designed to measure the heat release rate, total heat release, time to ignition, time to extinction, effective heat of combustion and formation of CO during the combustion process, as a function of sample thickness, sample density and the magnitude of the imposed radiative heat flux. The thermophysical properties of the surrogate material were either measured (solid density, void space, particle density, particle porosity) or extracted from the published data (heat capacity). The present surrogate RDF material was found to ignite easily, within a few seconds of the imposition of the incident heat flux of 40 kW m^?2, and then to reach rapidly the peak heat release rate of 110–165 kW m^?2. The deduced values of the critical heat flux, pyrolysis temperature and effective thermal conductivity are 9–10 (±2) kW m^?2, 280–310 (±30)° C, and 0.4–0.7 (±0.3) W m^?1 K^?1, respectively, depending on the material density. The effective heat of combustion of the RDF was estimated as 15.3 MJ kg^?1. The material produced 1 kg of CO per 18 kg of dried RDF, mostly during smouldering phase after the extinguishment of the flaming combustion. These results indicate that dried RDF pose significant fire risks, requiring that fire safety systems be implemented in facilities handling RDF. Copyright © 2005 John Wiley & Sons, Ltd.     

Fire performance and mechanical properties of acrylonitrile‐butadiene‐styrene copolymer/modified expandable graphite composites

The fire performance and mechanical properties of an acrylonitrile‐butadiene‐styrene (ABS) copolymer compounded with different expandable graphites (EG) and fire retardants were studied by using the limiting oxygen index test, the UL‐94 test, a mechanical test, and a thermogravimetric analysis. The ground EG treated with phosphoric acid and silane could have the great increase of the volume expansion ratio. The addition of the treated EG in ABS significantly enhances the fire performance but decreases the impact strength of ABS. ABS with the treated EG has a much higher impact strength than with the as‐received EG because of the smaller particle size of the treated EG and the better adhesion between the ABS and the treated EG. The addition of modified ammonium polyphosphate or decabromodiphenyl oxide/antimony trioxide can considerably improve the fire performance of ABS/treated EG composites because of a synergistic effect. The V‐0 grade (UL‐94) ABS composite with the limiting oxygen index of 32.5 can be obtained by adding small amounts of the treated EG and modified ammonium polyphosphate into ABS. Thermogravimetric analysis results indicate that the initial vapor release temperatures and the weight loss rates of ABS/EG composites are closely related to their fire performance and affected by the fire retardant used. Copyright © 2011 John Wiley & Sons, Ltd.     

The roles of standard cigarettes in assuring the ignition resistance of soft furnishings

Regulations for cigarette ignition resistance (CIR) of soft furnishings (beds and upholstered furniture) and less fire‐prone cigarettes have contributed substantially to the decrease in losses from cigarette‐initiated fires over time. Two standard reference cigarettes play key roles in mitigating these losses and in sustaining the effectiveness of the fire safety regulations as exogenous changes occur. SRM 1082 provides a uniform, durable supply of cigarettes for use in ASTM E2187 that assures manufacturers and regulators of compliance with regulations for reduced ignition propensity cigarettes; enables quality control of cigarette fire test performance; enables assurance of uniform interlaboratory test results; obviates effects on fire safety as tobacco crops and smokers change over time; and, when the original ASTM E2187 substrate material was no longer available, enabled adding a new, equivalent substrate. SRM 1196 provides a uniform, durable supply of cigarettes for assurance of consistent interlaboratory evaluation of the ignition resistance of soft furnishings using the mandated test methods; obviates possible unknown changes in soft furnishings' CIR due to the evolving ignition strength of the original test cigarette over time; and provided a test cigarette that was stronger than most cigarettes being smoked after manufacture of the original commercial test cigarette ceased.