Predicted abundances of gas-phase CS, HCS⁺, and CO withrespect to H₂ as a function of time. The curves correspond to the different physical conditions observed in the TMC1-C source with = 10⁻¹⁶ s⁻¹. Each curve (density) corresponds to a different position of Table 3 in Fuente et al. (2019). Colored boxes represent the agreement with the observations. The abundance of S with respect to H is depleted by a factor of 20 relative to the cosmic value.