The objective of this study was to reveal flame spread characteristics of the insulation material, expanded polystyrene (EPS) with different thicknesses under different environmental conditions (pressure and oxygen concentration). Experiments were carried out in small-scale flame spread experimental benches in the Tibetan plateau and Hefei, respectively, with EPS sample sheets inclined horizontally. Changes in the flame spread speed, average length of the pool fire, average maximum flame height, and maximum flame temperature in the surface flame zone were used to determine the effect of the plateau and plain environments on flame spread characteristics. The results showed that with the increase in sample thickness, the values of these parameters increased both in Lhasa and Hefei. The values of flame spread speed, average length of the pool fire, and average maximum flame height in Hefei were all larger than those in Lhasa, while the maximum flame temperature in the surface flame zone in Hefei was less than that in Lhasa for the EPS of the same thickness.

Summary The effects of sample width and ambient pressure on horizontal flame spread over horizontal rigid polyurethane foams are experimentally studied. A series of comparative experiments are conducted at two places with different altitudes in China. The sample surface temperature, spread rate, and height of flame are measured over a range of sample widths from 4 to 16 cm. Experimental results show that the horizontal flame spread rate decreases as the sample width increases in a negative power law at both two altitudes and the flame spread rate in the Hefei plain (at an altitude of 30 m) is larger than that on the Tibetan plateau (at an altitude of 3658 m) of the same width. The horizontal flame spread mechanism on the rigid polyurethane foam is analyzed qualitatively in comparison with the results of the flame spread rate of expanded polystyrene foams. The relationship between the dimensionless flame height (Hf/W) and the sample width (W) is obtained by using Froude number similarity. It is found based on the experimental data under two different ambient pressures that the average value of the exponent of the ambient pressure in the power law for the horizontal flame spread rate is about 1.9, which is in good agreement with the theoretical value 2.0. Copyright © 2014 John Wiley & Sons, Ltd.