Ensuring a sufficient smoke-free layer during fire incidents is one of the key factors for safe evacuation and effective operation of smoke control systems in buildings. In Russian practice, design guidelines often adopt standard values of 2.2–2.5 m for the clear layer height without detailed justification. However, experimental studies and computational fluid dynamics (CFD) simulations indicate that the smoke-free layer height is highly dependent on room geometry, fire load, ventilation configuration, and extraction rate. This paper investigates the influence of the smoke-free layer height on the performance of mechanical smoke control systems. A literature review of national and international standards and methodologies is provided, highlighting the lack of unified approaches to determining this parameter. Parametric calculations based on the methodology were performed for different values of the smoke-free layer height (from 1.2 to 2.9 m). The results show significant changes in key parameters of the smoke control system, including smoke layer temperature, density, exhaust volume flow rate, and fan pressure requirements. The findings emphasize that an increase in smoke-free layer height may lead to a decrease in exhaust temperature and fan pressure while improving evacuation conditions. The study contributes to more accurate design recommendations for smoke control systems, bridging the gap between normative methods and CFD-based approaches.