Natural disasters have inflicted serious damage on humankind from time to time. Some of the most severe disasters in Japan and many other countries are said to be earthquakes, which frequently trigger secondary disasters such as tsunamis, landslides, and fire accidents. In fact, most casualties in an earthquake are not due to the earthquake itself but to such secondary disasters. Therefore, it is essential to detect the occurrence of each disaster and gather additional real-time information in order to minimize the number of casualties. Considering this background, we concentrated on creating an effective system for propagating information on fire accidents swiftly using pedestrians' mobile phones, because we considered it easy to detect fire accidents among these secondary disasters. In this paper, we focus on establishing a configuration-free system for propagating fire alerts only by attaching an ad-hoc network device to the fire alarm generally installed in each house. Thus, we can collect information on fire accidents without configuring any personal location information. We evaluate how effective this system is in the event of fire, and the results show that we can estimate the location of fire with an error of <;20 m. This is accurate enough to locate a fire in order to obtain an overview of the situation.