Abundance of C₂H₂ with respect to n_〈H〉 obtained from the fiducial disk model. The white lines show the gas temperature contours for 180 K and 1000 K The gray contour depicts A_V = 8.5. The green dotted line shows the region from which 50% of the continuum emits at ~13.7 µm (representative of the v₅ fundamental band). The green solid line shows the region where 50% of the flux is emitted by C₂H₂ at 13.7 µm. The white dots indicate the grid points for which the chemistry is subsequently analysed in detail. The cyan contours depict where 20 and 99% of hydrogen is in the form of H₂.