Abundances as a function of time for selected species computed for dense cloud conditions (see Section 3.5) using three different chemical networks: udfa06 (blue dashed lines), osu-01-2009 (red dashed-dotted lines), and kida.uva.2011 (black lines). Dotted curves represent 2σ error bars on the abundances computed with the kida.uva.2011 network using uncertainty propagation in the reaction rate coefficients.