Flame spread definition

MATERIAL PARAMETERS CONTROLLING FLAME SPREAD 3.5.1 Definition... 

When a flame traverses a pre-formed combustible mixture which is at rest in a horizontal tube, a zone of intense reaction moves along the tube with a definite velocity. If the gas mixture is streamed through the tube at an appropriate rate, the flame front itself may be maintained stationary at the mouth. In either case the relative velocity of flame front and gas mixture is the same. If the speed of the stream is less than the rate of travel of the combustion zone, the flame performs the operation known as striking back. If, on the other hand, the gas stream emerges from the tube faster than the combustion is propagated, the flame spreads forth from the mouth... 

The measurements consist of flame spread over the surface and light absorption in the exhaust duct of the timnel. Test duration is 10 min. A flame-spread index (FSI) is calculated on the basis of the area under the curve of flame tip location versus time. The FSI is 0 for an inert board, and is normalized to approximately 100 for red oak flooring. The smoke developed index (SDI) is equal to 100 times the ratio of the area under the curve of light absorption versus time for the 10-min test duration to the area under the curve for red oak flooring. Thus, the SDI of red oak flooring is 100, by definition. 

The plenum concept has been so successful that many plenums contain abandoned cables where each cable can individually pass the smoke and flame spread requirements, but when added together, they can have a measurable fuel value. The next logical evolution in fire safety is to limit the overall fuel load in the plenum, which has led to the definition of a limited combustible cable [12], These cables have a maximum potential heat value of 3500 BTU/lb (NEPA 259) in addition to the smoke and flame spread requirements common to other plenum cables. As described earlier, the best way to minimize fuel load with a polymer is to use a perfluorinated compound, and in this case, both primary insulation and jacket benefit from this attribute [13],... 

The observation that polymer-clay nanocomposites have significantly lower peak heat release rates (PHRRs) when compared to the pure polymer [47] stimulated a dramatic effort focused on the evaluation of the flame-retardant potential of clay dispersed in polymer. The decrease in PHRR can be related directly to the decrease in the spread of fire from one combustible material to another. This affect is directly applicable to definition (1) above. Figures 8.1 and 8.2 contain a comparison of cone calorimeter results for a pure polymer and a nanocomposite of that polymer with montmorillonite. 

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