<p>During the process of inert gas injection for fire prevention and suppression in coal mines, the injection of inert gas into the gob area changes the gas atmosphere from an oxygen-containing environment to an inert gas atmosphere. This inevitably affects the coal spontaneous combustion process. This study employed a gas supply system with convertible gas sources and in situ infrared spectroscopy to simulate the dynamic transition process of the gas atmosphere during inert gas injection into the mine gob, and analyzed the impact of the altered gas atmosphere on the types and contents of functional groups in coal. The main conclusions are as follows: The change in gas atmosphere from dry air to nitrogen inhibited the oxidative consumption of methyl and methylene groups, while simultaneously restricting the oxidative formation of carbon–oxygen single bonds, carbonyl groups, and carboxyl groups; its effect on carbonyl groups was relatively minor. By calculating the inhibition rates of the abrupt atmosphere change on various functional groups during different oxidation stages, it was found that the inhibition rates for methyl, methylene, carbonyl, and carboxyl groups initially increased and then decreased with rising temperature, reaching a maximum at 130&#xa0;°C. Finally, the inhibition pathways of the abrupt change from a dry air atmosphere to a nitrogen atmosphere on the reactions of various functional groups in coal were revealed from a chemical reaction perspective. The conclusions drawn in this paper can provide theoretical guidance for underground inert gas fire prevention and suppression, and offer a new research approach for dynamically revealing the mechanism of inert gas inhibition on coal spontaneous combustion.</p>