Hazard studies related to Carbon Sequestration (CCS) and Enhanced Oil Recovery (EOR) lack of appropriate descriptive models of pressurized CO2 releases. The complex inherent phenomena linked to a rapid depressurization in addition to the generalized lack of approachable and targeted experimental data, makes current QRA procedure inadequate. In light of this, the proposed work aims at achieving two correlated targets. Firstly, the results of an experimental campaign performed on CO2 pressurized releases are proposed. Secondly, a source model for multiphase CO2 pressurized releases is illustrated in terms of filling existing gaps. The reported experimental campaign focuses on the estimation of useful parameters to be used in the modeling procedure namely the experimental discharge coefficient and the thermodynamic nature of the expansion transformation. Bulk and discharge orifice pressure and temperature profiles are illustrated, focusing on how a multiphase CO2 release alters main discharge parameters. The proposed modeling approach allows for the collection of details on the expansion degree of reversibility and heat transfer effects are inferred showing that ideal isentropic and isenthalpic paths are never matched. Its application well matches collected data and gives good prediction of the total discharge time. In addition, direct unobservable dynamics inside the closed tank are assessed, notably the instantaneous dense CO2 mass fraction and peculiar evolutions during phase change mechanisms in the liquid-vapor and solid-vapor domains. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.