Representation of the data of the full sample and models with constant pressure for [O iii] 88 µm/MIPS 24 µm as a function of ([C іі]+[O i])/[O iii] (top panel), and [O iii] 88 µm/MIPS 70 µm as a function of ([C ii]+[O i])/[O iii] (lower panel). Each model is represented with a color for the initial density, n₀, and a line style for U, and the lines follow the c_PDR, with the markers representing the proportions of 0%, 50% and 99%. The models displayed are calculated for an age of star-forming burst of 4 Myr. The gray points are the observed values for each pixel of the regions.