Grids of Cloudy calculations: model L_[C II]/L_TIR vs. H I and H₂ mass reservoirs in the C⁺, C⁰-emitting regions, total H₂ mass, and L_[C II]/L_[O I] behaviour (last column) in terms of metallicities of Z = 0.05, 0.1, and 1.0 Z_⊙ (from top to bottom) and for a range of G₀ and n_H, the initial hydrogen density. The colour coding in each figure is log n_H/cm⁻³ which increases from 1.0 (green) to 4.0 (purple). A range of G₀ is set by varying log r_in/cm from 21.3 at the top right of the grids (large dots) to 20.0 at the bottom left of the grids (smaller dots). These r_in values cover a range of log G₀ of 1.25 to 4.06 (Sect. 5). The Cloudy models are run with a source luminosity of 10⁹ L_⊙. Thus, the output masses should be scaled likewise (see Appendix A for details). The models are run to log N(CO)/cm⁻² = 17.8 (A_V ∼ 10 mag) for these grids.