Methanol column densities calculated with the spherical 1D static chemical model using the physical structures derived for the cores B213-C2 and C6 (left panel), C10 (central panel), and C16 (right panel). The yellow, green and grey squares represent the results of the models extracted at 10⁵, 10⁶, and 10⁷ yr. The column densities observed towards B213-C6, C10 and C16 are shown as dark blue, red and light blue in the left, central and right panels, respectively.