THE ANALYSIS OF THE TRANSITION FROM SMOLDERING TO FLAMING IN POLYURETHANE CONTAINING ASSEMBLIES REPRESENTATIVE OF UPHOLSTERED FURNITURE
Knapp, Graham Michael
Stoliarav, Stanislav I
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The smoldering and ignition of upholstered furniture is the leading cause of loss of life in accidental residential fires. Due to these fatal incidents, a new smoldering apparatus experimental setup was designed and built to investigate the temperature profile, the gaseous products, and the probability of transition from smoldering-to-flaming in polyurethane foam based upholstered furniture when subjected to a high intensity cartridge heater representative of a cigarette. The measurement locations in which the gaseous products and the temperatures from smoldering combustion were determined (2.5 – 22.5 cm above the heater) and the materials that made up each upholstered furniture assembly (cotton and polyester fabrics and battings with both fire retardant or non-fire retardant polyurethane foams) were both varied during the tests to investigate the specific gaseous quantities compared with temperature readings as a smolder front propagates and how varying materials affect the transition from smoldering-to-flaming, respectively. On average, the rate in which the smolder front propagates near the end of the test is 2 times faster than the rate at the start of the test. All tests performed produced large amounts of Carbon Dioxide and Carbon Monoxide, which is representative of 95% of the Oxygen that was consumed. During the moments directly before the sample transitions from smoldering-to-flaming, there is a noticeable increase in Oxygen consumption as the distance from the heater increases past the smolder front and into the Oxygen limited pyrolysis zone. The anaerobic pyrolysis zone produces the combustible fuels required for transition, and once a substantial amount of combustible fuel is produced, the high temperature smoldering reaction ignites the fuel. In varying the materials used in each upholstered assembly, it was confirmed that the probability of transition increased substantially with the use of cotton fabric and cotton batting, while the use of polyester fabric and polyester batting greatly reduced the probability of transition. The presence of fire retardants in fabrics and polyurethane foam can greatly reduce (or even eliminate) the probability of transition, but when paired with cotton batting, higher levels of fire retardants (BS 5852 rated) were required.