Effect of the nature of fuel on the characteristics of fully developed compartment fires

Abstract

The coupling between the constituent reactions of a burning process, namely pyrolysis, combustion of volatiles, and (possibly) oxidation of char, is on the whole quite different for fires occurring in the open and for those that develop in an enclosure. Consequently, knowledge of the characteristics of free burning fires is of only limited value in studies related to compartment fire. Since the singe‐rout communication between the fire compartment and its environment, always assumed in classical fire studies, is not at all common in real world fires, great sophistication in the mathematical modeling of classical fires is rarely warranted. An examination of pool‐like fires and pile fires of noncharring fuels has shown that the severity of such fires in the fire compartment, as characterized by the so‐called ‘fire severity product’, decreases slightly with an increase in ventilation. The principal danger presented by these fires, however, is not so much to the fire compartment itself as to the surrounding spaces.An interesting feature of fires involving charring fuels, cellulosies in particular, is that the rate of consumption of fuel, the so‐called ‘rate of burning’, is practically independent of all process variables except ventilation. The severity of fires of cellulosics is, as a rule, much higher than that of fires of noncharring fuels. It exhibits a maximum at relatively low ventilations. From the point of view of spread of fire to the surrounding spaces, cellulosics are generally less dangerous than noncharring plastics. Fires involving cellulosics mixed with smaller amounts of noncharring plastics can be characterized as basically cellulosics fires, with a superimposed initial period of very high spread liability.