Abstract: When a fire occurs in public areas such as shopping malls, it's difficult for indoor personnel to determine their own location, and they will easily misjudge the fire situation, resulting in difficulty in safe evacuation. However, traditional identification means such as evacuation schematic diagram can only provide general advice, but cannot show dangerous areas, and the applicability of safe evacuation is low. In view of this situation, this paper proposes a passive positioning system for indoor personnel based on Wi-Fi probe, which uses Wi-Fi probe and passive positioning method to locate people in the area, it can generate the thermal map of regional personnel distribution and mark the fire danger area. This paper also puts forward the WCS-KNN positioning algorithm. The results show that the positioning accuracy of WCS-KNN algorithm is improved by 23.46% and the running time is shortened by 10.75% compared with other algorithms. The passive positioning system of fire personnel can determine the personnel distribution and the fire danger area when the fire occurs, and guide the personnel to evacuate safely by means of broadcasting and intelligent evacuation display screen, and can continue to work in the fire. The system has better applicability compared with the traditional evacuation means.

Key words: public safety, Wi-Fi probe, passive positioning, safe evacuation