Abstract: The fire behavior， ignition characteristics and smoke characteristics of XPS(extruded polystyrene) were studied experimentally with various distances and locations of the fire source under the mechanical ventilation velocities of 0， 0.6 and 1.2m/s. The experimental results showed that the flame spreading speed on the surface of XPS gradually increased and coking appeared earlier with the increase of wind speed. The XPS ignition time were nearly linearly related to the fire source distances under the same ventilation velocity and fire source location. The maximum ignition distance of XPS decreased from 0.2 m to 0.15 m with the increase of ventilation velocity from 0.6m/s to 1.2m/s when the fire source was perpendicular to the wall. In addition， the maximum temperature of smoke and the minimum variation of the concentrations of oxygen， carbon dioxide， and carbon monoxide were obtained when the ventilation velocity reached to 0.6m/s. Therefore， the XPS burning rate increased first and then decreased with the growth of ventilation velocity. When the ventilation velocity was low， the increase of oxygen concentration promoted the XPS combustion. The thermal inhibitory influence of new air on the XPS combustion was enhanced significantly with the further increase of the ventilation velocity， thus the XPS combustion rate reduced.

Key words: objective, interval particle, intervalextruded polystyrene(XPS), ventilation velocity, ignition characteristics, fire behavior, smoke characteristics