An equation of state for thermodynamic properties of humid gases, combustion gases, and CO2-rich mixtures typical for Carbon Capture and Storage (CCS) processes, the EOS-CG mixture model, is presented in this work. This model uses the mathematical approach of the GERG-2008 equation of state by Kunz and Wagner (2012), and presents new mixing parameters for mixtures of carbon dioxide, water, nitrogen, oxygen, argon, and carbon monoxide. The EOS-CG model covers a wide temperature and pressure range in the vapour, liquid and supercritical regions, and is valid over the full composition range. It improves the calculation of complex phase boundaries of binary and multi-component mixtures, where water and/or carbon dioxide is involved, as compared to established models such as the Lee-Kesler-Plocker equation, the Soave-Redlich-Kwong model, and the GERG-2008. (C) 2015 Published by Elsevier Ltd.