C¹⁸O(2−1)/C¹⁸O(1−0) intensity ratio as a function of the gas temperature determined using three different methods: peak of the ¹²CO(1−0) line (top), HCN(1−0)/HNC(1−0) line ratio method of Hacar et al. (2020) (middle), and the empirical fit based on the dust temperature described in the text (bottom). The data are color-coded as in Fig. 1, and the purple points in the bottom-right panel indicate the Orion A positions where the NH₃-based temperature estimate of Friesen et al. (2017) has been used. The dashed lines represent the expected line ratio under optically thin LTE conditions, and the ability of the data to match this curve reflects the quality of the temperature determination.