Model B, the three-stage shock model, for CH₃OH, simulating a shock. The 10 K cold cloud stage (left) is followed by a sharp increase in density and temperature to simulate a shock (middle) and then a post-shock stage (right), when the gas settles to the LTE conditions observed. The time axis represents the age of each component independently. The LTE components are separated based on their temperatures and densities. The components of each model are in dotted, dashed, or solid lines; blue lines are the model abundances in the gas phase, yellow the model abundances in the grain phase, and black the observed abundances calculated from the averages in Table 2. As C1 and C2 are warmer, we suggest they are still in the shock stage, whereas the cooler C3, C4, and C5 are in a post-shock state.