The operating theater is the environment inside the hospital that requires the greatest deal of attention in the choice of the devices for air supply, diffusion and recovery. The design of Heating, Ventilation and Air Conditioning (HVAC) systems dedicated to these environment plays a crucial role to drastically reduce the risk of infection for patients, in addition to the maintenance of adequate thermo-hygrometric comfort conditions for the medical team. As a result, a lower risk of sepsis has been reported thanks to a cleaner air injection in operating theaters. In this work, the authors have reproduced numerically the air distribution inside an operating theater, where a swirl diffuser system is present. The numerical results have been validated against the experimental data obtained during field campaign. The objective of the present work is to develop an effective and robust numerical model able to reproduce the fluid dynamics phenomena inside operating theaters.