Abstract: Thermal radiation ignition experiment of two groups of cotton with mass of 10 and 20g were carried out by cone calorimeter. The heat radiation intensity is 35,30,25,20,15,10,5,4,3 and 2kW/m² respectively. The heat release rate curve, total heat release curve, combustion residue morphology and residual mass were compared and analyzed. The results showed that when the cotton is burned, there is always smoldering at the same time. The peak of the heat release rate of open flame combustion is higher than the maximum value of the heat release rate of the smoldering under the same conditions, and increases with the increase of the scale. There is no peak in the smoldering heat release rate curve and the heat release lasts longer. The critical igniting heat radiation intensity of cotton sample with size of 100mm×100mm×24mm and mass of10g is2~3kW/m²; and that of cotton sample with size of 100mm×100mm×24mm and mass of20g is4~5kW/m². As the increase of bulk density and relative humidity of the sample, the critical igniting heat radiation intensity increases

Key words: cotton, heat radiation intensity, heat release rate, ignition criterion