The AutoReaGas code developed by TNO and Century Dynamics Ltd has been utilized to simulate the occurrence of a Vapour Cloud Explosion in a large fuel storage area. The sensitivity of the results to the main input variables has been investigated, together with the effect of fuel amount and fuel concentration inside the cloud. The marked sensitivity to several adjustable parameters, such as the turbulent modelling constant C-t, shows that the use of Computational Fluid Dynamics codes is not a straightforward task but still requires an adequate skill. From the whole set of computed results, some suggestions are derived, in order to improve the predictive power of the code.