Many chemical reaction systems exhibit input/output multiplicity characteristics and non-minimum phase behavior. These inherent characteristics are known to cause limitations in process operation, so it is useful to have some knowledge of these at the early design stage of a chemical reaction process. Focusing on inherently safer designs, this paper addresses a strategy for classifying the process operating region into distinct zones at the early stage of process design, based on stability/instability and minimum/non-minimum phase behavior analysis. The strategy is illustrated by two case studies, where the operating spaces of an isothermal CSTR and an exothermic CSTR are classified into zones with different characteristics. The results provide information that is very important for guiding process design and operation about how the inherent properties of a process change with changes in its operating conditions. (C) 2009 Elsevier B.V. All rights reserved.