Abstract: Ventilation is the main performance requirement in laboratory design, as it has to guarantee a safe and comfortable indoor environment. Standards and guidelines on laboratory ventilation often impose high ventilation rates increasing the energy need for ventilation. This research focuses on the steady-state distribution of temperature and contaminate concentrations in a real environment which was a function of several factors such as the position of air inlet and exhausts. Different distances between inlet diffuser and exit grill were investigated to determine the optimum distances between inlet diffuser and exit grill. CO2 is used as an indicator of the concentration of pollutants inside tested room. Room concentration patterns for a laboratory were simulated with Computational Fluid Dynamics (CFD) simulations by using (ANSYS 14) computer programs for various distances. The computational results were validated with design data due to Iraqi cooling code (setup temperature and temperature difference from head to foot level). The numerical results showed that the exhaust grills located near the ceiling resulted in lower pollutant concentrations than the corresponding exhausts near the floor.