Thermal Analysis of Vertical Upward Flame Spread and Dripping Behaviors of Polystyrene Foams at Different Altitudes

In order to reveal the effect of altitude on the flame spread and dripping behaviors of PS foams a series of upward flame spread experiments was carried out on the plateau area of Lhasa and the plain area of Hefei. It was found that, during the flame spread process, extinction occurred on the plateau for expanded polystyrene (EPS) and extruded polystyrene (XPS) foams while, on the plain, the flame spread could be well sustained and, at longer times, even acceleration was observed. Due to the increase of smoke generation, resulting in decreases of the flame heat flux and oxygen concentration in air entrainment on the plateau, the burning and heat transfer were not efficient in Lhasa, making extinction occur. A larger angle for the pyrolysis front of EPS and XPS on the plateau was another important factor promoting extinction. The mass of dripping PS in the pool fire zone was also studied for different thicknesses of PS at the two altitudes. The maximum dripping mass of EPS or XPS was much larger for thicknesses of 4 cm and 5 cm than for 2 cm and 3 cm, attributed to the melting PS dripping to the pool fire zone directly making the effect of attaching to the wall weaken.