Investigation on the effects of water mist and mechanical smoke extraction on fire combustion and smoke dispersion characteristics

The combustion characteristics and smoke dispersion behaviours of indoor fires have always been critical topics in the field of building environment. The effects of a water mist system and a mechanical smoke extraction system on fire source combustion and smoke spread characteristics were investigated through full-scale experiments. The results indicated that mechanical smoke extraction could accelerate fire source combustion, resulting in the highest flame height. It could effectively reduce indoor temperature and would raise the smoke layer height to approximately 1.7 m. In contrast, the water mist system would suppress fire source combustion, reducing the flame height and controlling the temperature rise below 2 m to within 25°C. Albeit with a 0.2 m decrease in smoke layer height compared to the mechanical smoke extraction system. When both systems were operating synergistically, the fire source combustion was significantly suppressed, resulting in the lowest flame height observed. The smoke temperature was notably reduced, limiting the overall temperature increase in the room to within 15°C. However, the combined effect of both systems accelerated the downward spread of smoke, causing the smoke layer height to fall below 1.0 m. These findings suggest avenues for further exploration in optimizing fire prevention and control strategies.