Sandwich panel performance in full-scale and bench-scale fire tests

Fire hazard assessments must be primarily driven by life safety variables. Concern is often highly focused on toxicity issues, since fire deaths, in the majority of cases, are found (in whole or in part) to be due to toxic gas inhalation. Procedures have recently been published by ISO, wherein the toxicity assessment of fire products is focused primarily on bench-scale testing for toxic potency (the ‘per-gram toxicity’). Yet hazards of products with regards to fire toxicity may be determined much more by their differences in burning rates than by any differences in toxic potency. Burning rates are not assessed in the pertinent standards (ISO 13344 and ISO TR 9122). For most product categories, techniques for predicting full-scale burning rates from bench-scale data are not yet in hand. Thus, today the best means of comparing actual, full-scale toxic fire hazards is the full-scale fire test, equipped with additional gas measuring instrumentation. Such an approach is not among the recommended methods of the international standards, yet it is the only one with innate validity. In the present work, a series of sandwich panel products were tested in a full-scale room configuration. Bench-scale comparison was made to the ISO 5660 Cone Calorimeter and the DIN 53436 tube furnace. The toxic gases were quantified in all cases by chemical analysis. The product which showed the best performance in the full-scale tests (rock wool insulated sandwich panel) did not achieve a good fire toxicity performance due to minimization of toxic potency. Instead, the successful performance was attributed wholly to reduction of burning rate. Bench-scale measurements of toxic potency were shown to lack relevance to reality in such cases where even the full-scale toxic potency is not a determining factor. © 1997 John Wiley & Sons, Ltd.     

Evaluation of passenger train car materials in the cone calorimeter

Recent advances in fire test methods and hazard analysis techniques make it useful to re‐examine passenger train fire safety requirements. The use of test methods based on heat release rate (HRR), incorporated with fire modelling and hazard analysis, could permit the assessment of potential hazards under realistic fire conditions. The results of research directed at the evaluation of passenger train car interior materials in the cone calorimeter are presented. These measurements provide data necessary for fire modelling as well as quantitative data that can be used to evaluate the performance of component materials and assemblies. The cone calorimeter test data were also compared with test data resulting from individual bench‐test methods specified in the FRA fire safety guidelines. The majority of the tested materials which meet the current FRA guidelines show comparable performance in the cone calorimeter. Copyright © 1999 John Wiley & Sons, Ltd.     

The influence of pressure on combustible and toxic properties of materials

Combustible and toxic properties greatly influence the application of materials in shipbuilding. These materials, especially plastics, create a serious toxic hazard during fire. Under fire conditions they decompose thermally, giving off considerable amounts of smoke and volatile toxic substances which cause a serious hazard to people overcome by fire inside a compartment.^1–3Lethal poisoning by the thermal degradation products of plastics has attracted the attention of many investigators to toxic hazards during a fire.^1,4 Underwater systems create, in particular, a serious fire hazard. Fire in a decompression chamber spreads in a different way to land fires and usually causes the death of the crew and complete destruction of equipment in the chamber. Theoretically, complete fire protection in a chamber could be achieved by the total elemination of combustible materials and their replacement by incombustible ones. However, from a practical point of view this is impossible. The general principles of materials selection used in underwater systems are defined by Det Norske Veritas.⁵ Unfortunately, these do not describe the methods of testing materials nor the criteria of materials selection. There is also a lack of information in the literature on toxic hazards under elevated pressures. This problem has been studied in detail with oxygen-enriched atmospheres in aerospace programmes,⁶ but because those studies are classified there is only fragmentary information in the literature.     

Flame-retarded polyurethane foam: furniture testing and specification

Upholstered furniture has been shown to present a significant fire hazard as it is relatively easy to ignite from small sources, such as cigarettes and matches, and burns rapidly producing large amounts of heat, smoke and toxic gases. Current UK legislation, controls and specifications largely concern the ignition resistance of materials and composites used in upholstered furniture. Ignition resistance is directly related to the probability of a fire starting in a given situation, but does not necessarily affect the fire severity and its consequences. The rate of fire development is governed by the rates of generation of heat, smoke and toxic gases and also by the rate of flame spread. At present there is no widely accepted way of determining these properties although tests to do so are being developed. This paper will review work on the burning behaviour of upholstered furniture, the development of combustion-modified polyurethane foams, methods of test for ignitability and performance specifications. It will also review the methods used to determine the rates of fire development and will indicate the possibilities for the future.     

Characterization of the burning behaviour of polymeric materials

Measurements of the limits of flaming and smoldering combustion and relative rates of burning under elevated temperatures and oxygen-depleted conditions have been used to characterize the fire behaviour of polymeric materials using a semi-empicical approach (based on scientific theory) in terms of Power Law Indices. The work was based on modified current tests; namely the Limiting Oxygen Index (ASTM D2863) at elevated temperatures and the Setchkin Flash and Self-Ignition Test (ASTM D1929) modified to operate in oxygen-depleted atmospheres and to record rate of weight loss. Results show that the relative flammability and rate of burning of materials can change markedly with fire environment, and confirms the need to test materials lunder conditions representative of those of the anticipated end-use hazard.     

A closer look at cause and effect in fire fatalities—The role of toxic fumes

Much has been learned about fire from laboratory studies on fire gases, but the idea of using a laboratory toxicity test to rank or rate materials with respect to fire safety has not proved to be a fruitful concept. ‘Toxicity’ standards or specifications are not an effective defense against the threat of toxic fumes in fire for reasons which are fundamental to the nature of fire itself. As a matter of public policy on materials standards, by far the best way of reducing the threat of toxic fumes and all other fire threats is by control and regulation of those materials properties or performance aspects which permit the elimination or moderation of fire. Some of the concepts discussed in this paper run counter to commonly held assumptions, and they are put forth for the purpose of stimulating open public discussion on alternative approaches to improved decision-making in fire safety.     

An assessment of PVC smoke

The conventional test method for evaluating the potential of a material to produce smoke in a real fire is the NBS Smoke Density Chamber. However there are major problems with this approach. These include foremost the fact that its results do not correlate with those of real fires. Furthermore, materials that melt and drip are able to achieve a favorable, but misleading, evaluation because a significant fraction of the sample escapes the burning process. Another problem is that the test takes no account of the role the rate or extent of material burning plays in controlling the smoke density in a real fire situation. The physical problems are solved by material smoke production evaluation techniques based on measurements from the Cone Calorimeter rate of heat release apparatus, which has been developed by the National Bureau of Standards. A smoke parameter has been developed, calculated from cone calorimeter measurements, which reflects the smoke hazard of a real fire. The smoke evolution characteristics for a series of rigid thermoplastic materials have been measured using the cone calorimeter and the smoke parameter concept. The results demonstrate that due to its tendency to resist ignition and to burn very slowly, PVC would produce very little smoke in a real fire situation. Of the 15 materials tested, the expected real fire smoke performance characteristics of PVC were superior to those of all other materials except one.     

Quantification of threat from a rapidly growing fire in terms of relative material properties

Equations have been developed which give the time available for escape or rescue, i.e., the time interval between detection and blockage of the escape route by smoke, heat or toxic gases. Alternative assumptions are explored concerning exponential vs power law fire growth and an extended fire plume vs uniform filing of the building. The equations are developed in such a form that the threat variable by which the fire is detected is not necessarily the same threat variable which first blocks the escape route. A number of interesting results have been obtained, and numerical values of key parameters measured in various test fires at Factory Mutual Research are tabulated. It is shown that for many polymeric fuels smoke will block the escape route well before temperature or toxicity becomes excessive. In such cases, if the fire, assumed to be growing exponentially, is detected by its smoke, the detector being located in the escape route, then the escape time, surprisingly, is independent of the smokiness of the material as well as the size and shape of the building. It is determined only by the growth rate constant (doubling time) of the fire and the sensitivity of the detector.     

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.     

几种不同保温材料燃烧性能的研究

保温材料作为国内现有建筑节能的主要材料,已在建筑行业得到广泛的应用,但保温材料种类繁多,其防火性能仍然存在较大的差异,本研究随机选取工程现场使用的各类保温材料,采用最新的燃烧性能试验方法以及试验仪器,对无机、有机、复合保温材料以及保温浆料的燃烧性能进行检测;试验得出有机保温材料燃烧性能差,无机保温材料属下不燃材料,复合保温材料决定于复合材料的燃烧性能。同时本论文综合以上实验结果对保温材料的使用提出相关意见和建议。     

The behaviour of commercially important diisocyanates in fire conditions. Part 2: Polymeric diphenyl methane-4,4′-diisocyanate (pmdi)

The behaviour of polymeric diphenyl methane-4,4′-diisocyanate (PMDI) is described when examined in a laboratory small-scale test for its reaction to fire (ease of ignition; heat release and toxic gas production). Full-scale real fire scenarios have also been staged to predict events if (1) drumstock PMDI and (2) sizeable pools of liquid PMDI become enveloped in a fire. PMDI requires a stimulus (e.g. heat) before it will ignite from an applied flame. It then burns in a self-sustaining manner for a few minutes, during which main emissions take place. Then a polymerization reaction begins, producing a low density non-burning residue, which progressively dampens down the burning events by blanket action. Residues of 30–80% sample weight were recorded. The major toxic gas produced is carbon monoxide, though free isocyanate is to be expected in the early stages of the fire, and hydrogen cyanide could be important, especially in well-developed fire conditions. Firefighters should therefore wear full protective clothing and fresh-air breathing equipment. Events when drums of PMDI are exposed to fire depend heavily on the characteristics of the containers, with some rupture steps proceeding with considerable violence. Drumstock PMDI should be stored separately from easily ignitable materials.     

Burning characteristics of materials

The feasibility of using a dynamic, i.e. multivariable, test procedure instead of the more usual single point tests has been investigated by determining the limiting conditions for burning. The rate of burning and the limiting conditions for flaming and smoldering combustion have been determined over a range of temperatures and oxygen concentrations. Results show that the relative burning rates of materials and also their relative combustion thresholds can alter significantly with changes in the tests environment.     

A new approach based on the modified FDS to numerically simulate cardboard box combustion under low pressure

To solve the limitation of the fire test in high‐altitude areas only detecting a limited number of low‐pressure environments, in this paper, appropriate modifications of the FDS source codes were made to generate a new simulator program for low‐pressure applications. Standard fire experiments with different counts (1, 2, 18, and 27) of cardboard boxes were numerically simulated under different pressure levels (101, 90, 75, and 64 kPa). The computation data show consistent trends with the experimental results obtained in the low‐pressure tank at Lang Fang. Furthermore, the simulation results have been examined to show typical quantitative relationships: (a) The peak mass burning rate divided by the fire base dimension is correlated with the product of the pressure squared and the combustible characteristic length cubed. The exponential indices for the 1‐box fire, 18‐box fire, and 27‐box fire are 0.31, 0.29, and 0.29, respectively. (b) The heat release rate and mass burning rate show a good linearity at each fixed environmental pressure. In conclusion, the modified FDS is validated to work well under low‐pressure conditions, which can provide a receivable means to conduct low‐pressure fire simulation and analysis.     

Evaluation of polymer combustion and fire retardance by using thermography

The temperature distribution in the condensed and gas phase during combustion of polymer materials in fire tests was measured by means of thermography. It is shown that these data are very useful for mechanistic rationalization of the diagnostically poor, fail-pass rating of most of these tests. Preliminary data were obtained for polymer materials, fire retarded or not, burning in the widely used Glow Wire and UL 94 tests. It is shown that the relative fire hazard and test rating may depend strongly on the combustion parameter on which the rating is based. Furthermore, detailed data on temperature distribution are helpful in eliminating intrinsic ambiguity of the UL 94 classification in the case of fire-retarded materials burning with dripping.     

Empirical prediction of smoke production in the ISO Room Corner Fire Test by use of ISO Cone Calorimeter Fire Test data

The combustion conditions in the ISO Room Corner Fire Test make it possible to predict full scale smoke production by use of prediction models and bench scale fire test data procured by the ISO Cone Calorimeter Fire Test. The full scale smoke production is governed by the type of material burning only if the rate of heat release is less than 400–600 kW. For higher rates of heat release, the smoke production is more governed by the combustion conditions. The influence of the combustion conditions on the full scale smoke production reduces the possibilities of smoke prediction to materials causing flashover within 10 min in the ISO Room Corner Fire Test. The smoke to heat ratio S_Q (m²MJ) was used to compare smoke production between the scales. In general, the comparison revealed that the smoke yield was significantly less in full scale than in bench scale, especially for the plastics. Plastics do yield more smoke than wood based materials in both scales, but the differences in full scale are not as extreme as indicated by the bench scale smoke data. No simple correlations between the scales seem to exist. Multiple regression studies on empirical smoke prediction models show that bench scale fire parameters can be used to predict full scale fire performance. A quite accurate empirical smoke prediction model is presented for the group of materials which caused flashover within 10 min. The model predicts the full scale rate of smoke production at a rate of heat release of 400 kW. The presented results might be used to assess the fire safety hazard of visible smoke, but benchmarks of smoke hazard do not seem to exist. Thus further studies and agreement on safety levels and principles are needed for general visibility analysis concerning fire safety engineering purposes. Copyright © 1999 John Wiley & Sons, Ltd.     

A study on fire behaviour of combustible components of two commonly used photovoltaic panels

Photovoltaic (PV) modules are installed in some modern buildings for generating renewable energy. When a building catches fire, burning PV panels can contribute to an already very hazardous environment. Two common polycrystalline silicon PV samples A and B were selected with their chemical composition analysed by the Fourier transform infrared spectroscopy with justification by X‐ray photoelectron spectroscopy results. Sample A was confirmed to be a silicate product with polyurethane adhesive, and sample B has epoxy resin and is likely to have flame retardant as claimed. Thermal analysis by heating the samples was carried out using thermogravimetric analysis and thermogravimetric analysis coupled with infrared spectroscopy. The fire behaviour was then studied by a cone calorimeter under radiative heat fluxes from 10 to 70 kWm^?2. Three key parameters representing flashover propensity, total heat release per unit area and smoke toxicity hazard were obtained from the cone calorimeter tests for ranking the thermal and smoke hazards. The thermal hazards of both PV samples are low, at least during the early stage of a fire without flame acting directly on the sample. However, vast quantities of smoke were emitted from burning PV panels under high heat fluxes. Copyright © 2016 John Wiley & Sons, Ltd.     

磷酸硼对樟子松的阻燃影响

采用磷酸硼对木材进行改性处理,测定了处理后试材的阻燃性、抗流失性、吸湿性、力学性能.研究结果表明,磷酸硼处理后试材,吸药量达到20.47 kg/m3以上时,垂直燃烧实验可达到到F-0级水平；通过灼烧实验,磷酸硼处理的木粉在500℃灼烧时残留率可达到97.997％;此改性剂具有较好阻燃性能和一定的抗流失性,常压下磷酸硼处理的樟子松试件LRV为50.28％；木材顺纹抗压强度平均下降了 8.67％,无明显变化;木材抗弯曲压强度平均下降了 27.95％.但磷酸硼阻燃剂在高湿条件下有一定的吸湿性,使用性能有待改进,并应注意采取防护措施.     

Toxic gas and smoke measurement with the British Fire Propagation test. I: Test conditions

No standard method has been developed for measureing the evolution of specific toxic gases from building lings when involved in fire. The British Fire Propagation test (BS 476 Part 6) operated in an instrumented room has been proposed for this purpose previously but has not found general acceptance. It is considered further in this report, which investigates the movement and measurement of smoke and specific fire gases under different conditions of room stirring and the effect of the latter on fire propagation indexes. Stiring has been found to have no statistically significant effect on fire propagation indexes provided that the effects of this on calibration of the apparatus are taken into account. Stirring also had little effect upon smoke production per se. Under unstire conditions smoke and toxic gases stratify in the same layer early in the test, and measurement of their production at any single room location will be subject to the location, the way the room influences stratification and how the room is instrumentee, as well as by the prpduct performance. Under stirred room conditions smoke and toxic gases are evenly distributed and product performance can be assessed more simply from concurrent measurements of fire, smoke and toxic gas parameters. The latter procedure is proposed for obtaining relative data on building linings and for examination in further studies for correlation to room and corridor burns.     

Mathematical modelling of fire development in cable installations

In 1996 DG XII of the European Commission (Research and Development) approved a 3 year project on the fire performance of electrical cables. Within this FIPEC project, a major part of the work involved correlation and mathematical modelling of flame spread and heat release rate in cable installations. The FIPEC project has developed different levels of testing ranging from a small‐scale, cone calorimeter test procedures developed for cables and materials, a full‐scale‐test procedure based on the IEC 60332‐3, but utilizing HRR and SPR measurements, and a real scale test conducted on model cable installations. Links through statistical correlations and mathematical fire modelling between these levels were investigated and the findings are presented in this paper. These links could form the scientific foundations for standards upon which fire performance measurements can be based and for new fire engineering techniques within fire performance based codes. Between each testing level correlation, numerical and mathematical models were performed. All of the models were based on the cone calorimeter test method. The complexity of the models varied from correlation models to advanced physical pyrolysis models which can be used in CFD codes. The results will allow advanced prediction of cable fires in the future. Also a bench mark was established for the prediction of cable performance by means of data obtained from the constituent materials. Copyright © 2002 John Wiley & Sons, Ltd.     

Studies on the Thermal Behavior of Polyurethanes

The number of fires appear to be increasing all over the world with some big fires started from burning sofa polyurethane foam (PUF). The general public is quite concerned about the risk of fire due to the extensive use of polyurethane-based materials. Better understanding of the fire behavior of the materials would provide guidelines on fire safety provision. The first step is to review the thermal decomposition mechanisms of polyurethane under different environmental conditions, which will be reported in this paper. Recent studies on the thermal decomposition kinetics and thermal stability of polyurethane are described. Thermal decomposition and combustion reactions of polyether-polyurethane and polyester-polyurethane in air and nitrogen atmospheres investigated by using thermogravimetry analysis will then be outlined. The kinetic processes of polyurethane decomposition studied by the model fitting method are discussed. Polyester-polyurethane was found to be thermally more stable than polyether-polyurethane. The presence of oxygen would significantly affect the breaking down of the polymeric chains. Fire retardants for polyurethane are also briefly reviewed. Results are useful for developing fire retardants for polyurethane-based materials with better fire behavior.