Combustion behavior of upholstered furniture. Important findings,practical use,and implications

“Combustion behavior of upholstered furniture (CBUF) ‐ Fire Safety of Upholstered Furniture ‐ EUR 16477 EN” was initiated by the European Commission (EC) since a major contributor to fire deaths in Europe was upholstered furniture. The EC and the participating research partners formulated this project to provide a scientifically sound basis for a European Union Directive. The aim of the directive was to improve fire safety in Europe as well as removing barriers to trade and creating a harmonized open market for upholstered furniture. The furniture directive never came through, but the project reached a significant understanding of how furniture burns, how furniture composition affects the heat release rate, and how well or poorly different models predict full‐scale test results and the developing hazard to people. The results were published as a book and presentations were made at several conferences. This article is a summary of some of the important findings in the CBUF project. It presents guidance for the design of low flammability upholstered furniture and the extent to which small‐scale test results can be used to predict room fire behavior. It presents test procedures and experimental data. However, much of the work that has been conducted is not presented in this article. In particular, background data and reasoning are omitted or reduced in favor of the results and conclusions.     

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.     

CBUF model II applied to exemplary NZ furniture (NZ-CBUF)

In the comprehensive EC-sponsored initiative, CBUF (combustion behaviour of upholstered furniture), three models were developed for furniture fire prediction. The second of these models, CBUF model II, is based on an area convolution technique with expressions of burning area over time determined for furniture types. In this paper, the CBUF model II was applied to a set of exemplary New Zealand (NZ) upholstered furniture items. CBUF Model II was not found to predict with goodness the combustion behaviour of the NZ upholstered furniture. Copyright © 2001 John Wiley & Sons, Ltd.     

Fire and upholstered furniture

Both ignition and rate of fire development tests are required to determine the fire performance of upholstered composites. Current practice uses small-model specimens for ignitability tests but rate of burning tests are usually carried out on actual furniture. This paper discuss small- and large-scale tests for upholstered furniture.     

An overview and experimental analysis of furniture fire safety regulations in Europe

The regulation requirements for upholstered furniture are nationally defined and lead to very different safety levels across Europe. This paper studies the fire performance of upholstered furniture across Europe and demonstrates the differences in the fire safety of sofas in different countries. Real sofas were purchased over Europe and tested first alone then for several of them in a room scenario. The fire performance of such upholstered furniture is related to their constitution and possibly to the improvement of their performance by physical and/or chemical means. Results are presented from a performance point of view and not focusing on the different technical solutions that can be envisaged, such as fire barriers or flame retardants. The results clearly show the effect of stricter regulations, not necessarily on the maximum heat release but mainly on the time available to escape, which is critical in many fire scenarios. Such regulations may have a positive effect, but they have to be performance-based, evaluated properly, and implemented considering market surveillance.     

Full‐scale study on combustion characteristics of an upholstered chair under different boundary conditions—Part 2: Ignition at the backrest top

The objective of this work is to investigate the effects of both boundary conditions and ignition positions on the combustion characteristic of a combustible item in a room. A series of full‐scale experiments were carried out in an ISO 9705 fire test room with an upholstered chair at three typical locations, i.e. the middle of side wall, room center and room corner. Here, ignition was achieved through a BS No. 7 wooden crib at the top of the backrest. The results show there were two peak heat release rates (HRRs) when the chair is at the room corner. However, when the chair was placed at the room center, only one peak HRR was observed. In addition, the peak HRR for the chair at the room center, about 800 kW, was much higher than that of the chair at the room corner, about 600 kW. Taken together with earlier work, in which the igniting crib was placed on the chair seat, the results show that the ignition positions, as well as the boundary conditions, influence the combustion behavior of upholstered furniture in a room. Finally, it is suggested that the chair burning would develop more slowly when it is ignited at the backrest than at the seat. Copyright © 2011 John Wiley & Sons, Ltd.     

Influence of Ignition Sources on Heat Release Rate in the Furniture Calorimeter

When measuring the production rates of heat and smoke of upholstered furniture the ignition source must not influence the test results. In this paper variations in the strength, application time and geometry of the ignition burner used in the furniture calorimeter are studied. Results from replicate furniture calorimeter chair test show that the burning behaviour is almost independent of the burner intensity in the applied regime. Tests on six different furniture items were performed in the furniture calorimeter. The test objects were exposed to three intensity levels of ignition source. The sources were: a large propane burner giving 30 kW during 120 s and a smaller propane burner used at two levels of heat output, 1.7 and 5.8 kW during 90 s. The results showed that the burning behaviour of the furniture was very similar regardless of which burner was used. This was especially evident when the time regime between 50 and 400 kW was studied. The length of this period is a measurement on how quick untenable conditions are developing in a single, well-ventilated compartment.     

Experimental study on water spray suppression on burning upholstered chair in an enclosure with different application times

The objective of this work is to investigate the effects of the application time of water spray on the burning upholstered chair in an enclosure. A series of experiments are conducted with the same water flow rate in an ISO 9705 fire test room in which a water spray system is installed. Several identical upholstered chairs are used in the experiments with the application times 20, 25, 30, 40 and 45 s after the ignition of upholstered chair, respectively. The results show that there is nearly an exponential relationship between the peak heat release rates and the relative application times of water spray. It is also shown that there is a polynomial relationship between the relative time for the peak heat release rate and the relative application time of water spray. However, there is an exponential relationship between the whole relative extinguishing time and the relative application time of water spray. A sudden increase is detected before the decreasing of CO generation rates after the water spray is applied on the burning upholstered chair. The average temperatures of the upper hot smoke layer under the ceiling will generally be lower with the earlier application of water spray. Copyright © 2009 John Wiley & Sons, Ltd.     

Performance and failure mechanism of fire barriers in full-scale chair mock-ups

The effectiveness and the failure mechanism of fire barriers in a residential upholstered furniture (RUF) were investigated by full-scale flaming tests on upholstered chair mock-ups. Six commercial fire barriers were tested in this study. Fire barriers were screened for the presence of elements that are typically used in fire retardants and the presence of commonly used fire retardants. For each fire barrier, triplicate flammability tests were run on chair mock-ups, where polyurethane foam and polyester fiber fill were used as the padding materials, and each chair component was fully wrapped with the fire barrier of choice and a polypropylene cover fabric. The ignition source was an 18 kW square propane burner, impinging on the top surface of the seat cushion for 80 seconds. Results showed all six fire barriers reduced the peak heat release rate (as much as ≈64%) and delayed its occurrence (up to ≈19 minutes) as compared to the control chair mock-ups. The heat release rate remained at a relatively low plateau level until liquid products (generated by either melting or pyrolysis of the padding material) percolated through the fire barrier at the bottom of the seat cushion and ignited, while the fire barrier was presumably intact. The flaming liquid products dripped and quickly formed a pool fire under the chair, and the peak heat release rate occurred shortly thereafter. Ultimately, the ignition of the percolating liquid products at the bottom of the seat cushion was identified as the mechanism triggering the failure of the fire barrier.     

Apparatus for investigating the burning and dripping of vertically oriented polyurethane foams

The burning and dripping behaviour of polyurethane (PU) foam is crucial for upholstered furniture fires due to the melting and dripping behaviour of the foam that results in a pool fire under the furniture, which enhances the combustion. The sample feeding vertical cone is developed to investigate the two-dimensional small-scale burning and dripping behaviour of vertically oriented PU foams where a constant irradiance is maintained at the exposed surface by means of automatic sample compensation. Seven different PU foams were investigated and classified as conventional foam or char-forming foam according to the observed surface phenomena during exposure to heat fluxes. The burning and dripping behaviour is found to depend on the foam density as well as the solid-phase char formation by the presence of fire retardant additives. The total mass loss rate and the dripping rate increase with higher foam density and with the presence of char formation. In contrary, the vaporisation rate is favoured at lower foam density and with the absence of char formation. Flexible foams of low density without the ability to form char tend to achieve low dripping rate where majority of the mass loss is via vaporisation, contributing directly to the gas-phase combustion.     

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.     

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.     

Evaluation of furniture-fire hazard using a hazard-assessment computer model

The Center for Fire Research Fire (Toxic) Hazard-Assessment computer model was used to evaluate the potential for hazard reduction by the modification of the combustion properties of upholstered furniture items in a residential occupancy. The potential benefits of these modifications are compared with the effects of variations in room size and construction to determine if they would be realized across a range of housing sizes and types. The results demonstrate the greatest benefit by the reduction of the mass loss (burning) rate of the item regardless of room size and even if the means used to reduce the burning rate results in an increase in smoke production and material toxicity. These results are intended as an indicator of potentially beneficial directions for further research and should not be taken as conclusive evidence of fact without experimental verification.     

Heat release testing of stacked chairs: Analysis of repeatability in a single laboratory

Fire testing of furniture has been a focus of much attention in the 1990s, particularly in terms of the heat it releases in real-scale fires. One aspect that has received insufficient attention is the case of stacked chairs, often found in places of assembly. Early data have shown that the fire hazard resulting from burning a stack of chairs is often much higher than would have been expected simply from the combined hazard of the individual chairs. A test has been designed, ASTM E1822, in which the flames from a propane gas burner (at 12 l min⁻¹) are applied to a vertical stack of 5 chairs for 80 s, and the important fire properties measured. This test was developed with the collaboration of two laboratories; the variables studied were: number of chairs in the stack and duration of exposure. In order to evaluate the repeatability of the method, one laboratory tested six different types of chairs, in triplicate, in a furniture calorimeter. The chairs were donated by different manufacturers for this purpose. A statistical analysis was conducted on seven properties (peak rate of heat release, total heat released, peak rate of smoke released, total smoke released, mass loss, time to peak rate of heat released and initial mass). The overall relative standard deviations for the properties studied ranged between 1% and 20%, which is adequate for a fire test. Thus, the repeatability study was successful. It is of interest that very poor correlation was found between mass loss and heat release, so that the highest fractional mass loss corresponded to the chairs with the lowest heat release rate. Additionally, there is also relatively poor correlation between heat and smoke release rates. The peak heat release rate of the stacks of chairs ranged from almost 300 kW to >1 MW, and the chairs lost between 4% and 40% of their initial mass; only one set of chairs did not release enough heat in any test for a room containing it to go to flashover. Thus, the results suggest that the potential exists for severe fires to develop when such chairs burn. © 1997 John Wiley & Sons, Ltd.     

Fire behaviour of upholstered furniture—an experimental study

A series of experiments for studies of flammability characteristics of upholstered furniture is presented. The series comprises 53 experiments on a reduced scale and 11 full-scale experiments in an extensively instrumented room. Results are presented from measurements of rate of heat release and smoke production. The experiments indicate that ignitability can be considerably decreased by careful choice of the upholstery materials.     

Estimating the impact of the mattress fire safety Standard 16 CFR Part 1633 on bed fire outcomes

Beds are a prevalent combustible in fatal fires in the United States effective 1 July 2007, the US Consumer Product Safety Commission promulgated a standard to severely reduce the heat release rate and the early heat output from mattresses and foundations when ignited by a flaming ignition source. This study estimates the Standard's success over its first decade using fire incidence, US population, and mattress sales data. The technique mitigates the influence of some exogenous factors that might have changed during this decade. The Standard is accomplishing its purpose, preventing approximately 65 fatalities (out of an estimated 95 fatalities in 2002‐2005) from bed fires annually during 2015‐2016, although not all pre‐Standard mattresses had yet been replaced. Compared to residential upholstered furniture fires, which were not affected by the Standard, the numbers of bed fires decreased by 12%, injuries by 34%, and deaths by 82% between 2005‐2006 and 2015‐2016. Per bed fire, injuries decreased by 25% and fatalities decreased by 67%, indicating that the severity of bed fires is being reduced.     

Influence of modern plastic furniture on the fire development in fires in homes: large‐scale fire tests in living rooms

About 80% of all fire fatalities in Germany occur because of fires in homes. It has been known for some time that modern materials (synonym for materials consisting mostly of synthetic polymers) tend to burn differently from older materials (synonym for materials consisting mostly of fibrous cellulosic substances) and it has been acknowledged that the amount of combustible plastics in homes has increased significantly over the last decades. To investigate the influence of modern furniture and ventilation conditions of fires in homes, a series of four large‐scale tests in two living rooms (LRs) with adjacent rooms (ARs) was performed by BAM and the Frankfurt fire service. Two LRs, one with older furniture and one with modern furniture, were tested twice each. Each test started with the ignition of a paper cushion on an upholstered chair. The influence of modern materials on the fire development was investigated, as well as the influence of the ventilation on the fire development. In all settings, an upholstered chair was the first burning item. Results of the test series show that fires in rooms with modern furniture develop faster than fires in rooms with older furniture. This is true for temperature development in the rooms as well as for smoke production.     

Soft furnishing fires: They're still a problem

Home fires in which soft furnishings were first ignited or contributed to fire spread cause a disproportionate share of US home fire deaths. Although the death toll from these fires is much lower than in the 1980s, the rate of death per 1000 reported fires has doubled. Data from the National Fire Incident Reporting System and the National Fire Protection Association's annual Fire Experience Survey were used to create national estimates of these fires and casualties. Including both fires in which upholstered furniture was the item first ignited and contributed most to fire spread, in 2013‐2017, upholstered furniture was involved in an estimated average of 7120 (2%) home fires per year, resulting in an average of 570 (22%) deaths per year. Mattresses or bedding were involved in estimated average of 10 530 (3%) home fires per year, resulting in an average of 370 (14%) deaths annually. In most of these fires and deaths, the item was first ignited. Smoking materials were the leading cause of these fires (20%‐26%) and associated deaths (52%‐54%). Various types of operating equipment and small open flames also play a role. Understanding the causes of these fires is essential to develop new strategies to prevent them.     

Effects of upholstery materials on the burning behavior of real‐scale residential upholstered furniture mock‐ups

Fire spread and growth on real‐scale four cushion mock‐ups of residential upholstered furniture (RUF) were investigated with the goal of identifying whether changes in five classes of materials (barrier, flexible polyurethane foam, polyester fiber wrap, upholstery fabric, and sewing thread), referred to as factors, resulted in statistically significant changes in burning behavior. A fractional factorial experimental design plus practical considerations yielded a test matrix with 20 material combinations. Experiments were repeated a minimum of two times. Measurements included fire spread rates derived from video recordings and heat release rates (HRRs). A total of 13 experimental parameters (3 based on the videos and 10 on the HRR results), referred to as responses, characterized the measurements. Statistical analyses based on Main Effects Plots (main effects) and Block Plots (main effects and factor interactions) were used. The results showed that three of the factors resulted in statistically significant effects on varying numbers of the 13 responses. The Barrier and Fabric factors had the strongest main effects with roughly comparable magnitudes. Foam was statistically significant for fewer of the responses and its overall strength was weaker than for Barrier and Fabric. No statistically significant main effects were identified for Wrap or Thread. Multiple two‐term interactions between factors were identified as being statistically significant. The Barrier*Fabric interaction resulted in the highest number of and strongest statistically significant effects. The existence of two‐term interactions means that it will be necessary to consider their effects in approaches designed to predict the burning behavior of RUF.     

Effect of flame heat flux on thermal response and fire properties of char‐forming composite materials

This study evaluates the effect of flame heat flux on the prediction of thermal response and fire properties of a char‐forming composite material. A simplified two‐layer flame model was developed and incorporated into a heat transfer thermal model to predict the thermal response and fire reaction characteristics of a burning material. A typical char‐forming material, E‐glass reinforced polyester composite, was used in the study. A cone calorimeter was used to measure the fire reaction characteristics of the composite. The flame heat flux in a cone calorimeter test setup was estimated using the simplified flame model. Thermal response and fire property predictions with and without the effect of flame heat flux were compared with experimental data obtained from the cone calorimeter tests. Results showed that the average flame heat flux of the composite in a cone calorimeter was 19.1 ± 6 kW/m² from model predictions. The flame had a significant effect on the thermal response and fire properties of the composite around the first heat release peak but the effect decreased rapidly afterwards. Copyright © 2012 John Wiley & Sons, Ltd.