Abstract: To investigate the effect of CaCO₃ on gas explosion suppression under CO₂ inerting conditions, gas-solid combined explosion suppression experiments using CO₂ and CaCO₃ were conducted in a 60 L constant-volume combustion chamber. At a CO₂ volume fraction of 2%, the effects of different CaCO₃ particle sizes (6.5, 15, and 75 μm) and mass concentrations (10, 20, 30, and 40 g/m³) on gas explosion pressure and flame propagation were investigated. The results showed that: ① Peak gas explosion pressure was lowest at a CaCO₃ particle size of 15 μm. As CaCO₃ mass concentration increased, peak gas explosion pressure first decreased, then increased, and finally decreased, reaching its minimum at a CaCO₃ mass concentration of 40 g/m³. ② At a CaCO₃ particle size of 15 μm and a mass concentration of 40 g/m³, the gas explosion flame front was relatively smooth, the flame expansion range was the smallest, and the overall flame propagation velocity was low. ③ Considering the changes in peak gas explosion pressure, flame propagation morphology, projected flame area, and flame propagation velocity, CaCO₃ suppression effectiveness did not increase linearly with decreasing particle size or increasing mass concentration, and an optimal parameter combination existed. Under inerting with a CO₂ volume fraction of 2%, suppression was optimal at a CaCO₃ particle size of 15 μm and a mass concentration of 40 g/m³. These results provide a reference for selecting appropriate CaCO₃ particle sizes and mass concentrations under low-concentration CO₂ inerting conditions.