Structure of the thermal explosion limit

In a closed system an explosion limit is the transition region which separates the regions of slow and explosive reactions with respect to initial conditions. In the present paper the characteristic features of chemical reaction in the transition region are investigated for thermal explosion. The critical phase trajectory of the system contains an unstable integral manifold. Initial conditions corresponding to this trajectory can be understood as the explosion limit. An equation determining maximum temperature rise on the critical trajectory is obtained. The transition region can be divided into regions of slow and explosive transient regimes. The transition region is characterized by the extrema of induction period and degree of reactant consumption which correspond to a maximum reaction rate.