We present recent results based on a homogeneous analysis of the DEep Spectra of Ionized REgions Database (DESIRED), a compilation of about two hundred high signal-to-noise ratio optical spectra of Galactic and extragalactic HII regions and other photoionized nebulae. We show important insights and caveats about the effects of electron density inhomogeneities and their impact on the temperature structure and metallicity determinations in ionized nebulae. In particular, we demonstrate how internal density variations can be critical for the analysis of infrared fine structure lines, such as those observed by the JWST in local star forming regions, which can lead to significant underestimations of metallicity if not taken into account. Another interesting result from the DESIRED analysis refers to the Cl/H ratio in HII regions, for which we find evidence of its uncoupling with O/H, suggesting nucleosynthetic differences between both elements. We are extending our homogeneous analysis by including data from some 1000 spectra of extragalactic HII regions from the literature with direct electron temperature determinations. With this enlarged sample we will check and generalize the results obtained with DESIRED and recalibrate strong line methods to estimate metallicities under different assumptions about nebular structure.
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