Different regions where H₂¹⁸O is expected to show lines sufficiently isolated from H₂O. These lines are not seen in the spectrum, compared a H₂¹⁸O slab models assuming the same best-fit parameters as H₂O in these regions, assuming a ¹⁶O/¹⁸O of 550. The models have been multiplied by 5 for visibility. The H₂O slab models are based on the best-fit parameters presented in Table 1 per wavelength region.