Reliable monitoring for fires is essential for the safe operation of underground mines. Usually, the parameters of interest are heat and products of combustion. Since products of combustion, such as carbon monoxide and smoke, are carried along by the ventilation, they are easily detected by fixed-point sensors at some distance from the source. However, the detection of heat must be accomplished close to the source if rapid information is required. This paper reviews distributed temperature-measuring systems that can detect heat sources anywhere along their continuous length. These systems use distributed thermocouple, thermistor, resistive, or fiber optics effects. An in-mine test was conducted at the U.S. Bureau of Mines Lake Lynn Laboratory to assess the performance of an advanced state-of-the-art distributed fiber optics system to a slowly developing coal and/or conveyor belt fire. The data show that the distributed fiber optic temperature sensor system may work well for underground fire detection applications.