An experimental estimation of ignition temperatures of wood by radiation

In order to clarify the ignitability and ignition temperature of timber which is exposed to fire, ignitability tests were carried out on eight species using the ISO ignitability apparatus. The species tested were shinanoki (Tilia japonica Simk.), harigiri (Kalopanax pictus Nakai), yachidamo (Fraxinus mandshurica Rupr. var. japonica Maxim), asada (Ostrya japonica Sarg.), nanakamado (Sorbus commixta. Hedl.), kabanoki (Betula spp.), todomatsu (Abies sachalinensis Mast.), and ezomatsu (Picea jezoensis Carr.). The specimens were heated at irradiance level of 20, 30, or 40 kWm(-2). Surface temperatures were measured by thermocouple and by radiation thermometer. A positive correlation was observed between the ignition time and density of wood specimens at each irradiance level. The ignition time was significantly affected by moisture content of the wood at irradiance of 20 kWm(-2). On the other hand, at irradiances of 30 and 40 kWm(-2), the ignition time of wood could be predicted from its density. Average ignition temperatures were 391, 331 and 329degreesC at irradiances of 20, 30 and 40 kWm(-2), respectively. These values were higher than 260degreesC, which is generally used for the ignition temperature of wood in the fire endurance test. Since the difference in the surface temperatures at ignition measured by thermocouple and by radiation thermometer was about 10 K, the ignition temperature can be easily estimated by radiation thermometer.