Ignition and flashover of reduced scale compartments with timber ceilings

Abstract

Experiments on reduced scale compartments with timber ceilings and floors were conducted to investigate the ignition of the ceiling and growth to flashover. Pool fires of various sizes were ignited and measurements were made of temperature in the plume and ceiling jet, and mass of the timber ceiling and floor. The compartment geometry was also systematically varied. The results showed that ignition of the ceiling occurred when the measured temperature at ceiling level was between 328 °C and 347 °C. This aligned with intermittent flame impingement on the ceiling from the initiating fire. Following ignition of the ceiling, in most cases the fire subsequently spread across the ceiling resulting, ultimately, in ignition of the floor. It was found that duration of preheating of the ceiling (by the ceiling jet) strongly influenced flame spread. In some cases, ignition occurred, but did not result in continuous flame spread across the ceiling – in these cases it was found that the ceiling jet was cooler due to wider geometry of the compartment. The data were compared against existing correlations from the literature, and it was found that existing methods may be used to predict whether ignition of the ceiling may occur and the conditions for flashover.