Locations of gas phase volatiles in the 0.1 M_⊙ disk embedded in a 1 M_⊙ envelope. The different colors indicate the different regimes where various volatiles are found in the gas phase: blue (H₂O, CO₂, and CO), red (only CO₂ and CO), and green (only CO). The accretion rate is indicated at the top. The arrows are indicating three different regions as indicated in Fig. 1: water photo-dissociation region defined by A_V = 3, warm inner envelope, and the disk surface (yellow line assuming T_gas = T_dust).