Most of the time, we live indoors within a confined space. So, it is very important to have a good indoor environment, especially in terms of air quality. One of the major factors affecting indoor air quality is the airflow profile. Computational fluid dynamics (CFD) can be used as an effective technique to simulate and study the indoor environment. In this study, the airflow profile in an indoor space with a ventilation layout (Layout-1) has been simulated and analysed using CFD, and the results were verified using Grid Convergence Index (GCI). A grid-independent solution must be reached to remove the mistake caused by the numerical solution in the simulation. To achieve this, a hexahedral mesh is refined by an iteration procedure at a ratio of greater than 1.2 each time. Grid convergence for the velocity profile was evaluated quantitatively using a Grid Convergence Index (GCI) that takes grid refinement into consideration. Due to computational limitations, a 10% GCI tolerance has been accepted for the current investigation. The tolerance factor was attained by the velocity field GCI. After achieving the required GCI values and monotonic convergence criteria for Layout-1, the medium grid was used to simulate the velocity profile of another ventilation layout (Layout-2). The velocity profile of Layout-2 was analysed and compared with Layout-1 at section Y = 0.5 m. Both layouts exhibit high velocities near the inlet, yet the mid-section remains a critical area with low airflow, especially in Layout-2. Layout-1 demonstrates superior airflow near the outlet, enhancing overall ventilation efficiency.