we will show the predictions of models similar to that of Kunth et al. together with the predictions of models for the chemical evolution of the solar region, under different assumptions about the production and nature of nitrogen, and we will compare them with the DLA data.

The chemical evolution model for dwarf irregulars
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We are using here the same model adopted by Kunth et al. (1995) which is aimed at describing the evolution of IZw18, namely of an object presently having a strong burst of star formation which induces a galactic wind.

The main features of this chemical evolution model are the following:

1\) one-zone, with instantaneous and complete mixing of gas inside this zone,

2\) no instantaneous recycling approximation; i.e. the stellar lifetimes are taken into account,

3\) only one intense burst of star formation is assumed to occur,

4\) the evolution of several chemical elements (He, C, N, O, Fe) due to stellar nucleosynthesis, stellar mass ejection, galactic wind powered by SNe and infall of primordial gas, is followed in detail.

If G$_i$ is the fractional mass of the element i, its evolution is given by the equations described in Marconi et al. (1994). $$\dot G_i(t) 