Operating room is critical environment that require ventilation for comfort and to control hazardous emissions from patients and staff. The ventilation system of a hospital operating room is used to provide comfortable and healthy environment. The healthy environment can be achieved by minimizing the risk of contamination through filtration and air distribution scheme. This paper involves numerical study for different ventilation systems studying the impact of dynamic characteristics of air on the indoor air quality by using (CFD) techniques. Five different configurations ventilation systems based on Hospital guidelines standards conditions are applied on a selected model to evaluate the efficiency of ventilation systems in minimizing the risk of postoperative infection. It was concluded that the fourth configurations (laminar airflow (LAF) and exhausts from low level at two sides exhorts) which matching with Germany and ASHRAE Standard are the most efficient which satisfies the comfort conditions and provides protection against infection.