The bench-scale test widely used to evaluate whether a burning cigarette will ignite（点燃） upholstered furniture may underestimate the tendency of component materials to smolder 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 scrutiny. 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 solely on the so-called cigarette-smoldering-ignition test.

The new research identifies changes to this test that might make it more realistic-representative of a "near-worst-case scenario." The modifications, 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 foam for furniture flammability testing-a challenging, longstanding priority of standards developers, regulators and fire researchers. Such a standardized foam would help in comparing flammability data from different laboratories.

In the current setup for the test, two fabric-covered foam pieces are positioned like seat and back cushions on a small solid wood support structure. A lit standard reference cigarette (one certified by NIST to burn consistently***) is placed in the crevice formed by the two pieces. To pass, a fabric covering or barrier material under test must prevent the burning cigarette from igniting the underlying 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 impedes air flow and, as a consequence, inhibits 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 Celsius higher.

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