This study considers the use of sensors to ascertain the safety of individuals in times of disaster, with the focus on the sensor power source and particularly on a means of obtaining a stable power supply for the RFID tags used as sensors. Although button cells are generally used as power sources for RFID tags, we investigated the use of temperature difference power generation (TDPG) by thermoelectric conversion elements for this purpose, with the power generated by the difference between skin temperature and external temperature. Comparison with button cells confirmed that TDPG can provide the same level of active drive for RFID tags.