Calculated abundances as a function of time for a standard dark cloud model (parameters from Agúndez & Wakelam 2013). Solid lines use the KIDA kida.uva.2014 ratefile (Wakelam et al. 2015) and dashed lines the UMIST RATE12 ratefile (McElroy et al. 2013). In both cases a subset of reactions involving HCCO is introduced, although its calculated abundance remains below the range plotted. The horizontal thick lines indicate the observed abundances in Lupus-1A.