The pressurised metered dose inhaler (pMDI) is the most widely used drug delivery system for asthma treatment. Over decades the pharmaceutical community has aimed to enhance system efficiency by paying particular attention to novel formulation development through experimentation. Fundamental understanding of the underlying physical phenomena that governs the aerosol source characteristics is much less advanced. In this work we describe a Computational Fluid Dynamics (CFD) simulation of the pMDI plume source. The use of a two-phase flow model and a new atomisation model is illustrated for a formulation with 10:90 % w/w ethanol-HFA134 in 50ul valve and actuator nozzle with an internal diameter of 0.3 mm. The model is implemented within a CFD simulation of the resulting aerosol plume in a USP-Induction Port (IP) linking the flow conditions inside the actuator to the plume source characteristics. The CFD results show how plume velocity reduces over a relatively short distance due to the high rate of momentum transfer with the inhaled airflow.