The dependence of initial pressure for the autoignition temperature about flammable liquid

Autoignition temperatures of flammable liquids have been measured by many researchers. Many data by the ASTM method have been reported especially. However, a fire sometimes happened at chemical plants due to the autoignition of the flammable liquid though it was dealt with under the lower temperature than this measured data by the ASTM method. Because, the autoignition temperature is not the value specific to the material, but it is different corresponding to the measuring condition, the device and the method. Actually, the data reported by one literature is often different from the data reported by another literature. Then, the author paid attention to the initial pressure for the measurement of autoignition temperature. The autoignition temperature of decane was measured by using a round bottom flask in a closed vessel. The autoignition temperature decreased with the rise in the initial pressure. AIT in 0.40 MPa was 192 $^{\rm o}$C that was lower than AIT in 0.10 MPa by 10 $^{\rm o}$C, and the ignition delay time was over ten minutes. The thermal explosion theory was applied. It is shown that the ratio of AIT difference increased in proportion to the logarithm of the ratio of initial pressure. Measured AIT about decane fitted this relationship well