In advanced water-cooled nuclear reactors, the passive safety systems are preferably used to achieve enhanced safety during accidental conditions. The passive containment air cooling system (PCACS) is one of the safety systems, which is used to remove heat from containment during accidental conditions like Loss of Coolant Accident (LOCA), Station Blackout (SBO), etc. PCACS uses the buoyancy-driven flow of air to remove heat from steel containment to avoid overpressure of the steel containment shell. It is important to understand the natural convection around the containment shell so as to evaluate the performance of PCACS. This paper presents the numerical investigation of the passive containment air cooling of a scaled-down experimental test setup presented in the previously published literature. The development of CFD model for evaluation of the performance of PCACS requires validation and thus experimental data is required. The results obtained from the numerical study and the published experimental data were found in the good agreement with each other. Air thermal hydraulics around the containment was studied based on the temperature, velocity, and pressure contours. This study provides a better understanding of the natural convection flow around the containment and helps in further numerical studies for actual scale containments.