The surgical site infection (SSI) is one of the most important infectious problems in hospitals which may be happened in 2. 6% of all surgeries. According to the literature, the primary source of SSI is the flakes released from the exposed skin of surgical staffs or patients. It is well known that appropriate VENTILATION strategy is the most effective way to control bacteria-carrying airborne particles responsible for SSI. In this research, the effect of the most dominant design parameter, namely inlet air velocity, on the ultra-clean VENTILATION (UVC) systems performance is evaluated in detail using the computational fluid dynamics (CFD). The results show an optimum value for the inlet air velocity which is mainly due to formation of a thermal plume over the wound tissue. This thermal plume protects the wound from contaminants deposition like a shield and may be disturbed at too high inlet air velocity. In addition, the effect of critical factors including the particle size the wound temperature, the operating lights boundary condition, and the existence of fixed and removable partitions on the optimum inlet air velocity is also investigated and discussed extensively.