The present study concerns the reliability and efficient design of full-scale automatic sprinkler systems for the fire protection of industrial facilities and process plants. In particular, sprinkler systems filled with pressurized air at idle state (dry pipe) were considered. In this prospect, Computational Fluid Dynamics (CFD) simulations were carried out in the framework of the OpenFOAM package to study the flow in the piping subsequently to the activation of one sprinkler head. A VOF (Volume of Fluids) approach was used to compute the air/water interface accounting for the compressibility of air (perfect gas), while turbulence was considered using the RANS-based k-e realizable model. In addition, specific routines were developed for the pump and sprinkler modelling, taking into account the phenomenon of choked flow when sonic velocity is reached at the outlet. The numerical results were first compared to measurements on a test bench of Gridded typology (scale 1 in volume) for the purpose of validation. Then, the influence of various parameters(i.e. initial pressure in the system, dimension of the outlet orifice) on the flow dynamics were assessed for sprinkler systems of Gridded and Tree typologies. In particular, the performance was evaluated in terms of time constant of the systems, i.e. the time necessary to reach steady-state water flow at the opened sprinkler head required to control a specific fire hazard.