Flux ratios of the H₂O 4₀₄−3₁₃ and CO 21−20 lines at ~125 μm calculated using compact and extended flux extraction regions (see text) corrected for contamination from other sources/outflows. Median values for the two configurations are shown by the dashed line. The light blue rectangle shows the parameter space between the minimum and maximum values of line ratios in the more extended configuration. The error bars reflect the uncertainties in the measured fluxes of the two lines, excluding the calibration error, which is the same for those closely spaced lines.