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Reduced Flammability of Upholstered Furniture Project

Summary:

The long term vision for this project is to enable the prediction of the burning behavior of residential upholstered furniture (RUF) based on the furniture construction, and the component material flammability and thermophysical properties. This capability will empower furniture manufacturers to design and manufacture low flammability RUF. These improvements will result in slower fire growth and significantly reduce the risk of flashover, which is associated with a majority of fire losses in residences. Currently the research is aimed at understanding furniture burning behavior, evaluating furniture fire blocking technologies, and maintaining a standard reference cigarette for smolder ignition furniture and mattress testing.

Description:

Objective - Develop the measurement science to (1) enable predicting fire spread and growth of upholstered cushions based on the material properties of the components used in their construction, (2) quantify fire losses due to flaming residential upholstered furniture (RUF), (3) maintain a standard for reducing RUF ignition by cigarettes, (4) quantify the effectiveness of fire blocking barrier fabrics, and (5) improve the understanding of smoldering and transition to flaming in RUF.

What is the new technical idea? The burning behavior of RUF is widely recognized as a dominant factor in the ignition, spread, and growth of building fires, particularly residential fires, which account for 80 % of fire deaths and property losses. The findings of a recent NIST Workshop confirmed the important role of flaming residential upholstered furniture in fire losses and provided a path forward to quantify its contribution. An analysis performed by John Hall of NFPA as a direct result of the workshop and submitted for publication provided the first quantitative estimate for the role of flaming RUF in fire losses when RUF is not the first item ignited. More recent work using a novel statistical analysis addressed this issue. Significantly, flaming fires (both as first and later item ignited) are estimated to be responsible for roughly half (a much higher fraction than previously estimated) of the amounts of deaths, injuries, and financial losses as those due to fires in which RUF is directly ignited by smoldering sources. This estimate, when combined with the Workshop conclusion that the vast majority of fire losses associated with RUF fires started by smoldering ignition occur after transition to flaming, confirms that the flaming burning behavior of RUF is the dominant factor in fire losses associated with RUF burning. Most prior attempts to curb the contribution of RUF to fire losses have consisted of limiting ignition, primarily smoldering ignition. As a result of concerns about the toxicity of flame retardants currently used in RUF, the only RUF fire standard in the United States (California Technical Bulletin 117­ 2000), that originally addressed the resistance of RUF soft fillings to small flame ignition, has been amended to limit the likelihood of smoldering ignition of filling materials by the covering upholstery fabric exposed to a smoldering standard cigarette (California TB 117 ­2013).

Due to the central role flaming RUF plays in fire losses, this project is focused on providing the understanding and tools required to reduce the ignition of, the growth rate, and the heat release rate of these flaming fires.

Fire testing if a full-scale RUF is impractical due to the large numbers and wide range of styles and materials, the rapid, fashion driven changes in upholstery materials, the relatively small numbers of a given RUF design and material combination that are generally produced, the high cost of testing, the time delay in obtaining test results once the customer has "designed" their RUF, and the shortage of capable test facilities.

The development of a technically sound furniture design tool based on characterized physical and combustion properties of the furniture components will be required by furniture manufacturers to produce RUF meeting potential future regulations based on limiting the heat release rate of RUF. Such a design tool will enable RUF manufacturers to identify the materials and configurations necessary to produce furniture with desired levels of fire performance. By designing furniture that is unlikely to generate sufficient heat release rate to initiate flashover in a room (to be characterized as part of an OA project supported by CPSC), the likelihood of flashover, with its associated fire losses, in residences will be substantially reduced.

The new technical idea is to develop capabilities to understand various aspects of the fire behavior of RUF and then combine these approaches to form the required tool. The potential of this approach was demonstrated during Phase 1 by applying it to the fire behavior of upholstered cushions, an important subcomponent of RUF. The Phase 1 results suggested that while heat release rates of full­scale mock­ups are correlated with results for similar composites in the cone calorimeter, the inability to measure fire spread rates in the cone calorimeter limited how well fire development on the mock­ups could be predicted. During the current phase (Phase 2) a small­scale fire spread test will be evaluated as a means for overcoming this limitation.  

This project is in direct alignment with the strategic roadmap on innovative fire protection.

What is the research plan? This is the second year of Phase 2 for this project. The landscape for the project has changed dramatically since its inception as discussed above. Five recent workshops and conferences have highlighted these issues. This public focus on RUF has vastly increased the immediate need for NIST findings as well as raising the visibility and scrutiny of our efforts. The public discussion, workshops, and individual discussions with workshop attendees from government and the private sector highlighted areas where additional research is required and provided an important opportunity to reassess our working hypotheses and research plans. While leading us to slightly modify our research focus, we have concluded that our current research directions are well matched to and appropriate for the rapidly changing regulatory and public perception environments. 

The research effort for FY 16 and beyond is broken into a number of Tasks. 

Task 1 will develop the measurement science necessary is to predict real-scale burning behavior of RUF from the point of initial sustained flaming to the time when the burning intensity has reached a point where it threatens ignition of nearby combustibles and/or leads to room flashover. The major working hypothesis has been that component analysis can be used as the basis for a design tool having sufficient fidelity to predict effects of design changes on fire spread and growth on RUF. This hypothesis was tested during Phase 1 by assessing the degree of correlation of small-scale composite tests (cone calorimeter) with the burning behaviors of four upholstered cushions mocked up in chair configurations. Upholstered cushions are typically an important component of RUF. This approach was chosen for initial demonstration in order to limit the wide range of geometric and material effects expected for actual RUF. Cushions were produced from a variety of commonly used padding materials, barrier fabrics, polyester fiber fill, and cover fabrics chosen to span a wide range of flammability properties. Statistical analysis by the Statistical Engineering Division revealed a strong correlation of maximum fire sizes on the mock-ups and various parameters derived from the cone calorimeter results. However, the periods required to reach the maximum values were not as well correlated since the cone calorimeter does not directly capture fire spread behavior. During FY16 the major milestone of this task will be to identify an appropriate small-scale fire spread test and assess its ability to improve the prediction of the real-scale fire spread behavior on the mock-ups. 

In addition to the work addressing the overarching goal of predicting the fire behavior of RUF, a number of more focused, shorter term efforts dealing with specific aspects of the RUF fire problem will be maintained from Phase 1. While these efforts are generating knowledge that contributes to the overall goal, perhaps more importantly, they are designed to answer important short term research needs and/or provide the measurement science to support tests and standards in use or under development. The following paragraphs detail these tasks. 

Task 2 will provide the technical basis for developing a test to characterize the burning behavior of cigarettes designed to reduce the ignition propensity far below those of the reduced ignition propensity (RIP) cigarettes in use today. The requirement for RIP cigarettes throughout North America has reduced deaths from these fires by about 30 %, but cigarettes remain the leading cause of direct ignition of RUF. Thus, meaningful reductions are possible by further reducing the propensity of cigarettes to ignite RUF. A major impediment to the development of such very low ignition propensity (VLIP) cigarettes is the lack of a suitable test for characterizing their ability to ignite smoldering in RUF. During FY 15 NIST has formulated a plan for developing the measurement science necessary to provide manufacturers with a metric they can use as they develop VLIP cigarettes and will initiate preliminary experiments. During FY 16 the goal is to organize a workshop designed to gauge interest in the topic and provide input from cigarette manufacturers, researchers, and code and fire safety experts. 

Concurrently, it is important to sustain the success of the current standard test method. Changes in the manufacture of the test substrate have potentially weakened the effectiveness of the fire safety regulations. During Phase 1, NIST developed a new substrate that captures the performance of the original substrate. A round robin study designed to assess how well the modified approach matches results from the original standard and its reproducibility was completed during the third year. The findings of this study, along with ballot text to effect the change in substrate, were shared with ASTM E05.15, the committee responsible for maintaining this standard. These changes have been balloted once, and a second ballot is awaiting a written report of a round-robin study. The results have been presented to ISO TC92 SC1 WG15, the committee responsible for maintaining the equivalent ISO 12863.  

Task 3 will use our improved understanding of smoldering behavior as the basis for suggesting possible changes to the decades-old standard fabric test used as the basis for smoldering RUF regulations with the goal of providing improved material property differentiation and reproducibility with a test that correlates with smoldering behavior on real-scale upholstery. The possibility of developing new approaches for characterizing the susceptibility of flexible polyurethane foam to sustained smoldering and for assessing the resistance of barrier fabrics to smoldering will also be explored. A second part of this task will determine the factors influencing transition from smoldering RUF to much more dangerous flaming combustion with a goal of providing approaches for reducing the likelihood of transition. This task was built on earlier efforts to develop a reference polyurethane foam (under CPSC sponsorship) for use in small-scale smoldering resistance testing. Initial studies began in FY 13 and have thus far demonstrated that the small-scale test is highly sensitive to the test configuration and various properties of the flexible polyurethane foam. Recent work has focused on improving reproducibility and characterizing standard foams used in revised California TB 117. The implications of these findings for existing standard tests of fabric smoldering propensity and RUF construction are being investigated. During Phase 2, studies are continuing with the goal of developing the measurement science necessary to provide a small-scale smoldering test capable of better differentiation between materials being tested (cover fabrics, barrier fabrics, or cushioning), providing improved reliability and reproducibility, and having a demonstrated correlation with observed smoldering behaviors on real-scale mock-ups and actual furniture. The goal is to provide recommendations to ASTM E05.15 and the NFPA Committee on Fire Tests by the end of Phase 2. 

Task 4 will develop the measurement science that enables selection and standardized testing of barrier fabrics (BF) for use in RUF. Fire blocking barrier fabrics appear to be the most promising technology for compliance with any future proposed flaming RUF regulation and appear to satisfy environmental, health, and safety (EHS) concerns as the performance of some BFs do not require the use of fire retardants. In FY12-FY13, more than 25 commercial BFs were tested for open flame resistance and characterized using a range of tools (e.g., TPP and cone calorimeter). Attributes critical to good performance were identified along with several tests that we believe will correlate with performance in full-scale RUF flammability tests. The testing guidelines and a database of performance values were published and shared at the recent CPSC meeting on fire barriers for RUF. During FY14, the focus was on smolder ignition resistance of BFs as a component used in RUF mock-ups. A number of barrier fabrics that were effective in reducing flaming fire heat release rates were found to significantly accelerate the development of smoldering in the flexible polyurethane foam used in the small-scale smoldering mock-up test. These findings have been published. During FY 15 the work has been extended to laminated barrier fabrics. In addition, a flaming barrier fabric test being developed by the state of California has been fabricated and applied to over twenty different barrier fabrics. Smoldering tests on real-scale chair mock-ups incorporate barrier fabrics as well as different FPUFs were originally planned for FY 15, but have been delayed by the unavailability of the NFRL. It still planned that these experiments will be completed during FY 15. Any future RUF flammability regulations will likely incorporate both open flame and smoldering requirements. During FY16, additional real-scale flaming and smoldering studies of real-scale cushion mock-ups will be performed in order to provide a data base for comparison with the results of earlier small-scale measurements of barrier fabric properties. The purpose is to identify a combination of small-scale tests that can be combined to predict barrier fabric effectiveness when used in actual furniture. The findings will form the basis for drafting a standard designed to characterize barrier fabric effectiveness for reducing the impact of smoldering and flaming RUF fires. The draft standard will be prepared in consultation with appropriate standards committees (e.g., ASTM E05.15, NFPA Committee on Fire Tests and ISO TC92 SC1). 

Task 5 entails quantification of changes in products and regulations on the losses from fires involving RUF. These studies are to be carried out by the EL Applied Economics Office. During Phase 1, these researchers performed a number of focused one-year studies that were identified by discussions within the research team. Phase 1 studies from FY12 and FY13 are available. During FY15, a study on the effectiveness of RIP cigarettes in reducing fire losses is being carried out. The topic selected for FY16 will leverage the findings from FY15 to focus on the potential impact of VLIP cigarettes on further reducing losses associated with fires involving RUF.

Barrier fabric test - No flame penetration through barrier fabric after 6 min. Photo credit: NIST
Barrier fabric test - No flame penetration through barrier fabric after 6 min. Photo credit: NIST

Start Date:

October 1, 2011

Lead Organizational Unit:

el

Facilities/Tools Used:

Staff:

Project Leader:  Dr. William M. Pitts

Associate Project Leader: Mauro Zammarano

More Information on Furniture Fire Research:

Less Fire-Prone Cigarettes

Topic: Flammability of Materials

Contact

General Information:
Dr. William M. Pitts, Project Leader
301-975-6486 Telephone

100 Bureau Drive, M/S 8665
Gaithersburg, MD 20899-8665