Comparison between the chemical kinetics model predictions and the empirically estimated abundances (see Table 3) for T Dra considering the case of a porous envelope. The black solid line represents ‘model-uv/x’, the green dotted line represents ‘model-x’, the grey dashed line represents ‘model-std’, the orange dash-dotted line represents ‘model-uv’. The blue solid lines shows the empirical estimations (HCO⁺ has a dark blue line for 2020 observation and a light blue line for 2024 observations), and the shadowed areas indicate a factor 2 for the uncertainties in the empirical abundances estimations.