Combustion experiments of polystyrene (PS) sheet in multiple dimensions were carried out on a small scale ISO 9705 cone calorimeter

which took 10cm×10cm plate as one unit and measured value of heat release rate. The flame began to accelerate spreading from the ignition corner to unburned region at the same speed upon ignition at right corner of PS sheet

and diffused in a geometry of regular fan. According to the shape of heat release rate (HRR) curve

combustion process was divided into three stages:ascending

plateau and declining stages. By analysis of heat release rate and combustion process

a linear relationship was found between total heat release and material area. Heat release in the ascending stage was about 77.83% of total heat release for burnings without a plateau. HRR curves were fitted with exponential function by combustion thermophysical parameters

such as heat release peak rate

peak time and heat release amount. The fitting results showed similar parameters which a mean of ascending stage was 0.003888 and mean of declining stage was -0.01178. Unified mathematical equation was obtained for ascending stage by taking 10×10-1 peak time of an experimental group as reference time. Both non-plateau peak value and peak time was calculated from correlation of heat release at ascending stage and total heat release. Further experiments verified that the mathematic model can predict heat release rate development of regular burning polystyrene sheet with and without plateau stage.