Reliable monitoring along an underground mine belt is of great concern because of combustibles, electrical apparatus, and friction. Belt entries are strategically located where a fire can have rapid and disastrous consequences. This paper reviews conventional distributed temperature-sensing systems based on resistive, thermistor, and thermocouple effects. These are shown to provide limited benefits. A new system tested by the U.S. Bureau of Mines, based on fiber optics and time domain reflectrometry, promises much better temperature and spatial resolution, faster response, inexpensive cable, longer distance, and comprehensive data analysis. Test results in a small, controlled, in-mine fire are given.