Vertical profiles of the emission surface for molecules other than CO isotopologues in the studied disks. Elias 2-27 is not shown due to a lack of data in other tracers. Black curves show the location of the CO isotopologues in the J = 2−1 transition for reference. The solid line is ¹²CO, the dashed line ¹³CO, and the dotted line C¹⁸O. Each coloured curve shows a different tracer, where the solid line is the mean value and the shaded region shows the dispersion of the retrieved data points within each radial bin. Grey lines mark a constant z/r of 0.1, 0.3, and 0.5.