Abstract: To reduce missed and false alarms in the early warning of coal spontaneous combustion caused by ventilation dilution and roadway geometric disturbances, full-scale roadway coal oxidation simulation experiments and thermogravimetry–Fourier transform infrared–mass spectrometry (TG-FTIR-MS) are employed. The detection timing characteristics of CO and associated gases in lignite, fat coal, and anthracite at an airflow velocity of 1.0 m/s, together with their correspondence with source temperature-zone migration, are investigated, and the longitudinal attenuation characteristics of near-roof CO for anthracite under different ventilation velocities (0.5–1.5 m/s) and roadway bend disturbances are analyzed. It is shown that coal rank significantly affects the detection timing characteristics of CO and associated gases, as well as the multi-gas temporal separation windows, during the early oxidation stage. Compared with lignite, the time for the CO volume fraction in anthracite to reach 24 × 10⁻⁶ and the initial detection times of H₂, C₂H₄, and C₂H₆ are delayed by 305, 94, 248, and 257 s, respectively. Correspondingly, the temporal separation windows of C₂H₄ and C₂H₆ relative to H₂ increase from 65 s and 103 s for lignite to 219 s and 266 s for anthracite. TG-FTIR-MS results indicate that the delayed detection timing of these gases is consistent with the overall shift of the oxidation and decomposition of active functional groups and of the main release temperature zones of typical gas products toward higher temperatures. At the transport level, ventilation conditions and roadway geometry jointly determine the spatial attenuation characteristics of near-roof CO and the reachability boundary of the warning threshold. In the straight roadway section, the longitudinal variation of dimensionless near-roof CO concentration is described by a longitudinal attenuation model, and the dilution attenuation coefficient is found to increase from 0.025 m⁻¹ to 0.035 m⁻¹ as the airflow velocity increases from 0.5 to 1.5 m/s. Additional turbulent mixing is induced by roadway bends, resulting in stepwise additional attenuation of near-roof CO concentration. The bend correction factors are calculated to be 0.770, 0.759, and 0.702 at airflow velocities of 0.5, 1.0, and 1.5 m/s, respectively, indicating that the additional attenuation effect becomes more pronounced at higher airflow velocities. Under weak-source conditions, this additional attenuation may reduce downstream CO concentration to near or below the warning threshold, thereby increasing the risk of missed alarms. Accordingly, a coordinated early-warning criterion based on “single-threshold triggering + multi-gas temporal consistency constraints” is proposed to reduce false alarms caused by abnormal increases in CO from non-fire sources. In addition, based on the reachability boundary of the warning threshold jointly determined by continuous attenuation in the straight roadway section and additional attenuation at bends, key monitoring sections are recommended to be arranged upstream of roadway bends, together with periodic parametric verification using the dilution attenuation coefficient and the bend correction factor, to improve the reliability of early warning for coal spontaneous combustion under complex ventilation conditions.