Experimental tools applied to the ignition study of spruce wood under cone calorimeter

Wood-based materials, which are more and more used in building construction, are often characterized by normative tests using the cone calorimeter. The ignition time and temperature, the mass loss rate or heat release rate are the most current measurements performed. The sample ignition can vary according to a large number of variables (humidity, density, scale sample, experimental conditions). The auto ignition phenomenon has been studied so far but opinions concerning the involved physical processes remain controversial. The purpose of the present work is to improve the study of thermal degradation of wood under cone calorimeter thanks to a dedicated experimental set up. This set up includes mainly, an infrared camera, enabling an accurate surface temperature measurement and a fast visible camera (3000 fps), used to highlight the “auto” ignition phenomenon. Surface temperature and mass loss rate evolution are presented for different heat flux expositions. The fast visible camera pictures showed an ignition piloted by the coil. The ignition occurs only above 55 kW.m^-2. When this external heat flux was sufficiently low, it was possible to observe the transition between pyrolysis solely and smouldering combustion for a sample surface temperature around 400 ° C.