Cumulative distribution functions display [NH₂D]/[NH₃] ratios for thesubsamples in Table 8. The distribution of 70 μm-weak sources is marked as a solid red line, the MIR-weak clumps are shown as a dashed blue curve, the MIR-bright phase as a dotted green line, and the compact HII regions as a dashed-dotted black curve. A deuterium fraction of NH₃ > 1 might result from passing through several dense and cold phases (see Sect. 4.2). A systematic error of the NH₃ deuteration is given by the difference between the NH₃ and NH₂D excitation temperature.