The air ventilation system is one of the supporting systems in the machinery of a warship. High temperatures in the engine room can lead to an unpleasant atmosphere and, in particular, to heat stress for the operating personnel. This heat stress was caused by the design of the engine room ventilation system not meeting the requirements due to the supply and exhaust fan. Under the given conditions, the air temperature reached 50 °C, higher than the standard 45 °C. Therefore, it was necessary to conduct a thermal analysis and redesign the ventilation system using a 3D CFD (Computational Fluid Dynamic). The parameters included temperature distribution, Hlow distribution, and Hlow velocity in the engine room of the Landing Ship Tank class warship when the engine load reached 50%, 75%, and 100%. The results obtained from the simulation were in the form of quantitative data such as temperature gradients and iso contours of the air in the engine room inside the warship. The data comprised velocity contours, temperature, velocity vectors, streamlines, and particle trajectories in space. The results of the CFD approach showed that the quality of the ventilation system in the engine room inHluences extreme conditions in the engine room.