Abstract: In engineering applications, the same content of fuel may not lead to uniform results in order to obtain the standard effective test fire, depending on the infrastructure conditions of the standard fire test room. Based on the specific test conditions, experimental research was carried out on the change of the linearity of the fire smoke characteristic curve caused by different toluene contents, and the volume ratio of toluene solution was 3.1%, 8.1% ,13.1%, respectively. The change law and the linearity of the ratio curve of m value to test time and m value to y value were obtained. The results show that by increasing the toluene content, the rate of smoke release could be quantitatively increased, and the linearity of the smoke characteristic curve becomes worse. For achieving the effective test of the smoke characteristics, the upper and lower limits of the toluene ratio in the fuel are limited by the linearity of the characteristic curve and the rate of smoke release.

Key words: n-heptane fire, standard fire test room, effective, m-t curve, toluene content