In the past, process simulators and accident simulators belonged to two distinct worlds. Dynamic process simulators were mainly applied to process control, process dynamic investigation and safety analysis (in terms of definition of emergency shutdown procedures). Accident simulators were related usually to the steady state accident investigation, as well as risk analysis and emergency preparedness and response. The manuscript shows how the coupling of process andaccident simulators represents an innovative and powerful tool to support the engineer’s activity in several fields, e.g. process planning, process control, accidentinvestigation, accident preparedness and response. The biunique interaction between these simulators allows investigating feedbacks and interactions among plants and industrial accidents. Actually, process dynamics affects the source term, i.e. the amount of released components and their chemical and physical properties, while the accident dynamics closes the loop by affecting the plant dynamics. The accident may have a direct effect on the plant dynamics (as in the presence of a heat source, e.g. a pool fire) or may have an indirect effect by influencing the integrity of field operators when the release of a toxic substance occurs. The manuscript shows the biunique interactions between a pool fire (originated by the release of a flammable liquid, as the consequence of an industrial accident) and the process itself.