The occurrence of a deep-seated fire in a pile of coal can be determined from the detection of CO, which is produced by the oxidation of coal. It is important to understand the physics of the rate of production of CO as it relates to the heating of the coal if an interpretation of fire size is to be made based upon co production. A significant application of this understanding is the detection of smoldering combustion prior to its breakout into flaming combustion in a pile of coal that surrounds a heat source, such as an overheated conveyor belt drive in a coal mine. Thermal transport and oxidation associated with coal particles is a nonlinear process based upon an arrhenius reaction rate for the o2 consumption. Thermal and mass diffusion are the primary mechanisms for a redistribution of thermal energy and oxygen in the coal pile of specified porosity. The CO production is related by an empirical expression to the local oxygen rate of consumption. In this U.S. Bureau of Mines study application of the model is presented to a 250- lb mass of coal (high-volatile bituminous coal) particles that is heated by an embedded cylindrical heat source maintained at 200 deg c. The evolution of the coal mass temperature and CO production rate were computed over a 29-h time period, as was o2 depletion. At any time in the induced heating of the coal mass, the local temperature, o2 consumption, and CO production are predicted. The model can be used to relate CO production rate to temperature increase within the coal pile.