Comparison of O, N, and S abundances obtained from B-type stars (green) and nebular (gas+dust) abundances derived from CEL and different values of t² (blue, red, and magenta). The violet box indicates O abundance obtained from ORLs in the Orion nebula by Esteban et al. (2004). The height of the boxes represents the uncertainties. Left and right columns correspond to the Cocoon and the Orion nebula. For sulphur, the resulting abundances using two different atomic datasets are indicated; for nitrogen in the Orion nebula, the abundances computed by assuming two different ICFs are shown. See text for more details.