In fluidization processes, the optimal contacting regime is dictated by the physical or chemical process in question, and can vary significantly from application to application. Even within the specified regime, it is often necessary to place constraints on the hydrodynamic behavior in order to meet operational requirements. While the ability to do this is very important, there is a lack in current technologies' ability to identify the operational state via direct measurement. This work adopts a local transient approach towards addressing this problem. In order to study the local fluid bed dynamics, needle-type capacitance probes were employed to gather local transient solids fraction data in a bench-scale bubbling bed. The time-series were then subject to analysis in order to extract various signal invariants. The parametric effects of axial measurement location, superficial gas velocity, and mean particle size were examined in order to identify favorable heuristic trends in the signal invariants with respect to global parameters governing fluidization quality (i.e., superficial gas velocity and mean particle size). This work demonstrates how these invariants then constitute the basis for a novel regime map based monitoring scheme for quality of fluidization with potential application to feedback control. (c) 2007 Elsevier B.V. All fights reserved.