Throughout the world, many coal fires are currently burning out of control. In the People’s Republic of China, ∼750 coal fires are burning and depleting a significant amount of the country’s energy supply. Emissions from the smoldering fires are polluting the soil, the groundwater, and the atmosphere. To protect the environment and the natural resources, the Chinese government has taken steps to control or extinguish these fires. In fact, the People’s Republic of China has been fighting these coal fires since the foundation of the country in its present form, following the Chinese fire-fighting manual from 1953.

To extinguish a fire—or hot spot, which the fire location is often called—its location must be known with a high degree of accuracy. Hot spots have been successfully located in Xinjiang and inner Mongolia, People’s Republic of China, by combining conventional and modern exploration methods. After the identification of a hot spot, phase terrain and thermal anomalies at the surface are surveyed by using the global positioning system and by thermal mapping with an infrared camera. Subsequently, detailed geological sampling and mapping provide the data to create two- and three-dimensional models of the fire. Our survey results of this initial phase revealed the location of several hot spots. The second phase concentrated on the geophysical survey of selected areas. for instance, magnetic investigations detect thermally demagnetized rocks, geoelectrical surveys measure the resistivity, which tends to increase in burned rocks, and seismo-acoustic surveys “listen to” the fires. As burning coal seams fracture along with the surrounding rock, microtremors are produced. Appropriately placed geophones can detect the source of such tremors. Investigations into coal fires include gas flux measurements and gas analyses to acquire data on air flow, air-flow velocities, and air pollution. By correlating all of the geophysical measurements and integrating them into a combined model, it is possible to determine the location and depth of a hot spot. In addition, the direction and rate of fire propagation can be calculated through interpolation and interpretation of several geophysical measurements. In this study, the results were confirmed by increasing downhole temperature measurements in holes that were drilled into the subsurface.