Calculated chemical equilibrium abundances as a function of radius for gaseous reservoirs that can act as precursors of some of the first condensates expected in C- and O-rich AGB atmospheres: carbon, TiC, and SiC dust in C-rich stars (top left, top right, and bottom left, respectively), and Al₂O₃ dust in O-rich stars (bottom right). Abundances correspond to chemical equilibrium calculations in which only gaseous species are included. The shadowed areas indicate the regions where the condensation of the different types of dust is thermodynamically favorable: from 1.6 R_* for graphite, 2.3 R_* for TiC, 2.8 R_* for SiC, and 2.6 R_* for Al₂O₃.