On fire ignition

Abstract

A large number of studies have been conducted on the subject of fuel ignition, reflecting the importance of ignition on the onset of fire. However most of the studies are conducted independently for either gaseous, liquid or solid fuels in spite that flaming ignition occurs in the gas phase for all fuels. In this work an attempt is made to present a unified view of the mechanisms leading to the ignition of fuels. The fact that flaming ignition is a gas phase process and that the combustion process that occurs in the gas phase is basically common for all materials. Consequently the mechanisms leading to gas phase ignition can be viewed as the anchoring mechanism for the ignition of any combustible material. The perceived difference in the ignition of gaseous and liquid or solid fuels is associated with processes related to the material gasification, and with minor differences in the process of gas phase ignition. The objective of this work is to provide a more comprehensive view of the process of ignition of gaseous and condensed fuels leading to a better understanding of the different flammability classifications and tests methods used to characterize ignition of different fuels. The ignition of a gaseous fuel is analyzed first, followed by the analysis of the particular characteristics of the ignition of liquid and solid fuels. Clearly, the differences are mostly of material gasification, either liquid evaporation or solid pyrolysis. Moreover, the different test methods used to determine the ignition characteristics of condensed fuels are based on determining the conditions in the condensed phase associated with the gas phase ignition not with the gas phase ignition itself. Although this approach is sufficient for practical purposes, ignoring the gas phase ignition can lead to incorrect conclusions related to material safety. © 2011 INTERNATIONAL ASSOCIATION FOR FIRE SAFETY SCIENCE.