This book systematically develops models of Spatially-varying transient processes describing thermal events. Such events should be entirely predictable for a given set of physical properties, system geometry, and initial-boundary conditions. For the various initial-boundary value problems which model a reactive thermal event, the following questions are addressed: 1. Do the models give a reasonable time-history description of the state of the system? 2. Does a particular model distinguish between explosive and nonexplosive thermal events? 3. If the thermal event is explosive, can one predict where the explosion will occur, determine where the hotspots will develop, and finally predict how the hotspot of blowup singularities evolve? Primary emphasis is placed on explosive thermal events and we refer to the three aspects of such events as Blowup - When, Where, and How.