An Experimental Study of the Effects of Natural Smoke Vent Areas on Smoke Layer Descent Characteristics in Large Spaces

In this study, the effects of smoke vent area on smoke layer descent in large-space fires were analyzed. A reduced-scale specimen (5.7 m × 4.56 m × 5 m) was fabricated by applying geometric similarity laws (scale ratio of 1/5.26) to the full-scale experiment (30 m × 24 m × 26.3 m). Experiments were conducted by varying the smoke vent area across five conditions, as determined by the theoretical reference values and current domestic fire codes. The results indicated that when the smoke vent area met or exceeded the theoretical reference value, the descent of the smoke layer was significantly delayed compared with the sealed condition, indicating a safe tenable height for evacuation. By contrast, vent areas below the reference values exhibited limited suppression effects. Notably, the condition based on the domestic code proved insufficient in suppressing smoke layer descent, confirming the need for a theoretical re-evaluation of smoke vent area calculations. These findings are expected to provide fundamental data for establishing optimized design standards for smoke vents in large-scale buildings.