CRITICAL CONDITIONS FOR UPWARD FLAME SPREAD AND COMPARISON WITH EMPIRICAL FLAMMABILITY INDEXES

We use recent advances in material flame spread physics to emphasize t hat empirical flammability Indices might be replaced by fundamentally derived parameters. Flame spread rates in upward wall fire situations can be described both for charring and non-charring materials by using a characteristics length scale, l(m), and a characteristic time, t(p) . The length scale, l(m), is related to the distribution and magnitude of the heat flux from the flames to the wall surface as well as to bu rning material properties and mixing processes in the turbulent wall f low. The same characteristic time, t(p), describes both the spread rat e, by the determination of ignition time or yet unpyrolyzed material, and the transient pyrolysis of the solid for situations where such pyr olysis can be approximated by a thermal pyrolysis model.