What is X in Livengood-Wu Integral?

One of the authors has found that the thermal ignition of hydrocarbons is controlled by a reaction loop initiated by the decomposition of H2O2, and proposed a universal rule describing the hydrocarbon ignition process. The universal rule was applied to answer the question "What is X in the Livengood-Wu Integral?", and to clarify the dependence of ignition delay times on pressure. X is basically the heat accumulated in the induction time of thermal ignition. However, CO satisfies the necessary condition of X because the formation rate of CO is proportional to the heat generation rate.