Evolution of the abundance of (ortho + para) NH₃ and NH₂D in shock environment, predicted by chemical models. Similar to Fig. 16, three conditions of pre-shock, shocked and post-shock gas are characterised by gas density and temperature, and extinction levels listed in Table 5. Contrary to the models shown in Fig. 16, each physical state is evolved for 0.1 Myr, with the latter two states having abundance levels initialised by the end values of the prior state.