Abstract: The study on law of gas product generation during coal spontaneous combustion is the ba‐ sis for conducting coal spontaneous combustion prediction and forecasting. The ultimate oxygen concentra‐ tion of coal spontaneous combustion is a key parameter for dividing the“three zones”of spontaneous com‐ bustion in goaf. To obtain the laws of gas production and oxygen consumption from coal spontaneous com‐ bustion in fully mechanized caving faces，coal samples were collected from the working face. Through pro‐ grammed heating experiments on the coal samples，the generation law of gas products with different oxygen concentrations with temperature was analyzed based on the experimental results. The natural ignition index gas was determined，and the CO gas threshold value was calculated through a mathematical model. A grad‐ ed warning system and threshold were established by integrating the natural ignition index gas and CO gas threshold value. By analyzing the oxygen consumption rate under different oxygen concentrations，and based on the variation of oxygen concentration with temperature，a fitting formula for apparent activation energy is established to obtain the apparent activation energy of coal spontaneous combustion under differ‐ ent oxygen concentrations. After comprehensive analysis，the Ultimate oxygen concentration index of the coal sample is determined. The research results are helpful in guiding the graded warning and precise pre‐ vention and control of spontaneous combustion in mines.

Key words: indicator gas, graded warning, program heating up, ultimate oxygen concentration, fire