Photo-dissociation region (PDR) benchmark. Temperature (T, right axis) and density of main hydrogen species (H, H⁺, and H₂, left axis) profiles as a function of column density (N) obtained for an impinging radiation flux of 10 G₀ propagating in a Z = Z_⊙ slab (see Sect. 3.2 for details of the model). Solid lines represent the numerical solutions computed with KROME at equilibrium (t ~ 1 Kyr), dashed lines represent the solution predicted by the emulator. Note: each point in the profile at a given N is treated independently by the emulator.