Demonstration of the LTE methodology used in this study for a region centred on ℓ = 33.3°, b = −0.02° in the 101.22 km s⁻¹ velocity channel. In the left column, the intensities of the three CO emission lines: COHRS ¹²CO (3–2) (top panel), CHIMPS ¹³CO (3–2) (middle panel), and CHIMPS C¹⁸O (3–2) (bottom panel) are shown. In the right column, the derived LTE properties: the ¹³CO (3–2) optical depth (top panel), the excitation temperature (middle panel), and the total ¹³CO column density (bottom panel) are also shown.