The bench-scale test widely used to evaluate whether a burning cigarette will ignite（点燃） upholstered furniture may underestimate the tendency of component¹ materials to smolder² when these materials are used in sofas and chairs supported by springs or cloth, National Institute of Standards and Technology (NIST) and American University researchers report in a new study. The study comes as regulations and methods for evaluating the likelihood that soft-furniture materials will ignite are undergoing scrutiny³. In November 2013, California removed an open-flame test from its furniture flammability testing law**-the de facto national standard since no national regulation currently exists-and now relies solely⁴ on the so-called cigarette-smoldering⁵-ignition test.

 

The new research identifies changes to this test that might make it more realistic-representative of a "near-worst-case scenario⁶." The modifications⁷, the researchers write, would make the test more consistent and, therefore, more useful for identifying "upholstery materials（室内装潢材料） most likely to prevent smoldering ignition."

 

In the same article, the research team reports guidelines for making a reproducible reference foam⁸ for furniture flammability testing-a challenging, longstanding priority of standards developers, regulators and fire researchers. Such a standardized⁹ foam would help in comparing flammability data from different laboratories.

 

In the current setup for the test, two fabric¹⁰-covered foam pieces are positioned like seat and back cushions on a small solid wood support structure. A lit standard reference cigarette (one certified¹¹ by NIST to burn consistently***) is placed in the crevice¹² formed by the two pieces. To pass, a fabric covering or barrier material under test must prevent the burning cigarette from igniting the underlying¹³ foam so that it does not smolder on its own, even after the cigarette self-extinguishes.

 

The researchers found that directly placing the test samples on top of the wooden support impedes¹⁴ air flow and, as a consequence, inhibits¹⁵ smoldering. They point out that the arrangement is not representative of furniture with cushions that rest on air-permeable substrates such as springs or cloth, which allows air to circulate and promotes smoldering.

 

The team introduced gaps between the foam samples and the underlying wood, permitting air flow. The adjustment increased-by up to threefold-the rate at which smoldering spread in the foam. It also generated significantly higher smoldering temperatures in the foam-as much as 400 degrees Celsius¹⁶ higher.

 

"Because it inhibits air flow, the current test apparatus¹⁷ may diminish the propensity¹⁸ for smoldering ignition," explains NIST's Rick Davis. "Creating gaps to increase air flow, and the other modifications we are suggesting-especially adoption¹⁹ of a reference foam-will enable more consistent smoldering behavior and help to minimize other causes of inconsistent flammability test results."

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