Influence of Seasonal HVAC Operation on Fire Detection System Performance in Summer and Winter

This study investigated the response characteristics of heat and smoke detectors using fire detection system (FDS) simulations, focusing on the effects of a ceiling-mounted heating, ventilation, and air conditioning (HVAC) system under different seasonal airflow conditions. The compartment dimensions were set to 2.0 3.2 2.0 m<sup>3</sup>/min, and a ceiling-mounted HVAC unit with four-directional air supply was installed at the center of the ceiling. A 0.5 0.5 m<sup>2</sup>/min fire source was located at the corner farthest from the entrance. Simulations were conducted for a total of six conditions, combining three airflow rates: maximum at 30.0 m<sup>3</sup>/min/min, medium at 25.0 m<sup>3</sup>/min/min, and minimum at 20.0 m<sup>3</sup>/min, under two seasonal conditions: winter with a temperature of 0.8℃ and relative humidity of 58.5%, and summer with a temperature of 28.5℃ and relative humidity of 74.0%. The results showed that airflow rate significantly influences the detection response time of heat detectors, with larger variations observed in the summer than in the winter. In contrast, the influence on smoke detectors was negligible. Under high airflow conditions, the supplied air from the HVAC system prevented combustion products from reaching the vicinity of the detector, leading to increased fire detection time. These findings indicate that in areas adjacent to HVAC systems, smoke detectors are more effective than heat detectors in early fire detection.