BPT diagram of sample of spectra of Galactic and extragalactic H II regions and star-forming galaxies compiled in DESIRED-E used in this study. The dashed line represents the empirical relation by Kauffmann et al. (2003) that we have used to distinguish between starforming regions and active galactic nuclei (AGNs). The dotted curves and vertical and horizontal lines represent filters applied by Amayo et al. (2021) to extract photoionisation models to construct their ICF scheme for star-forming regions.