As part of the large-scale development of Carbon Capture and Sequestration (CCS) infrastructures, this thesis focuses on the analysis of the state of art on modelling of the consequences related to accidental or controlled releases of CO2 into the atmosphere, with the aim of understanding whether the techniques available are able to simulate this phenomenon. After a description of release characteristics, such as the formation of solid particles of CO2 and the possible formation of the dry ice bank, specific models were presented with their capability to predict the thermo-fluid dynamic behaviours of CO2 in a broken pipeline, to define the source term and to predict the near- and far-field dense dispersion of CO2.