Cloudy modeling of the interior structure of a typical H ii region. The Hα emission (red) traces fairly closely the ionization fraction (f_ion, blue) as a function of radius, while the [O i] (green) is predominantly emitted in the outer shell of the nebula. In this way, it is apparent that very little of the Hα emission is co-spatial with the [O i], a key assumption in our model. At the outer edge of the nebula, the intensity of [O i] rapidly drops together with the electron temperature T_e (orange).