Comparison between the predictions of models listed in Table 5 and the cumulative column densities derived in TMC 1. In this figure, we have selected N(CO)/N(H₂), N(HCO⁺)/N(CO), N(HCN)/N(CO), N(CS)/N(H₂) and N(CS)/N(SO) to explore the parameter space, where N(CO) has been derived from our observations as N(CO) = 600 × N(C¹⁸O) and N(H₂) = A_V(mag) × 10²¹ cm⁻². The observational points are indicated with squares and different colors correspond to the three observed cuts as follows: black for TMC 1-CP, red for TMC 1-NH3 and blue for TMC 1-C. Dashed red lines indicate A_V = 3 mag (C⁺/C/CO transition region), A_V = 5 (translucent cloud) and A_V = 10 mag (dense region).