This paper describes the simulations for two test conditions. Empty room simulation and other one for to decidethe quantity of ventilation requirements needed to moderate the risk of flammability when leakage is present ofrefrigerants from large chillers inside rooms. Room size is 376 m³ is simulated using computational fluiddynamics. The chiller capacity is 2640 kW. Cooling solutions is carbon dioxide (CO2) natural refrigerant (R744) formachine room and for empty room R-290. The paper presents the required safety standards, and refrigerantconcentration sensor is involved to activate ventilation system for an emergency to dilute the refrigerantconcentration with fresh air. The results of the simulation data established ventilation standards needed formoderate the risks of refrigerant leakage inside given rooms