AbstractIn order to study the ignition capability of welding slag to polystyrene extruded board of B2 grade, the ignition process was simulated by changing the splash direction of welding slag, the initial distance between the extruded board surface and triangular iron, as well as the shape of extruded board. The results show that the ignition capability of horizontal and vertical welding slag at the distance of less than 6cm are similar, while at the distance of 6cm, the ignition capability of vertical welding slag is higher than that of horizontal welding slag. The shape of the extruded board (blocks or chippings) has little influence on the ignition capability of vertical welding slag within the range of 6cm. It is believed that the conclusions of this study can provide some references for fire investigation related to the ignition capability of welding slag to polystyrene extruded board.