Density plots for [Fe II]λ5.3403  μm/[Ar II]λ6.9853  μm vs H₂S(5)/H₂S(3) (top) and W₈₀ for the H₂ S(5) line vs H₂S(5)/H₂S(3) (bottom) for all sub-samples. The vertical lines represent the mean H₂S(5)/H₂S(3) predictions of the shock models from Kristensen et al. (2023) for velocities of 5, 10, 25, and 50 kms⁻¹ (different colours) and densities of n_H = 10³ (dotted lines) and n_H = 10⁶ cm⁻¹ (dashed lines).