A type-C all-glass concentric pneumatic nebulizer (CPN) widely used for sample introduction in inductively coupled plasma mass spectrometry is characterized. Although the fundamentals of the spray formation in CPN and (ICP-MS nebulizers in general) is similar to mechanical engineering nozzles, the specific design, the geometry, dimension, and nominal flow regimes of the former require separate characterization. As investigated in this paper, the well-known Nukiyama-Tanasawa (NT) correlation leads to erroneous size prediction. In this study, an optimization to the NT model together with characterization for spray velocity is presented. The efficiency of the nebulizer under different gas and liquid flow rates is determined, and finally the characterization results of size and velocity are employed into a maximum entropy principle model to predict the velocity and size distributions of the sprayed aerosol.