Abstract: The cabin containing power cable in the utility tunnel has high fire risk. In case of fire, it is very easy to cause a major fire accident. The author has developed and built a solid fire test platform for the utility tunnel, and carried out experimental research on local application and total flooding application of water mist fire extinguishing system under different working conditions. The results showed that: for the electric cabin of the utility tunnel, the water mist fire extinguishing system should adopt total flooding fire extinguishing mode, when it is really necessary to use local application fire extinguishing mode, the fire zone and adjacent zones shall be sprayed with water mist at the same time, and ensure the length of the fire extinguishing section and the intensity of the system spray. During fire extinguishing, ventilation and smoke exhaust system and door and window openings seriously affect the water mist fire extinguishing performance in case of fire, it shall be closed in time. When total flooding is applied, properly increasing the spray intensity of the system is the key to ensure the high fire extinguishing efficiency of water mist.

Key words: fire fighting, fire fighting, utility tunnel, fire characteristics, utility tunnel, fire characteristics, total flooding application fire extinguishing mode, total flooding application fire extinguishing mode, local application fire extinguishing mode, local application fire extinguishing mode, water mist fire extinguishing system, water mist fire extinguishing system