Impact of the cleaning process on the SED of high-z dusty sources. The SED of the extragalactic sources is modelled by a modified blackbody with T_xgal = 30 K and a spectral index β_xgal = 1.5, for five different redshifts from 0.5 to 4. The original SEDs (solid line) are normalized to be 1 MJy sr^-1 at 857 GHz. The SEDs at various redshifts after the cleaning process are shown with dotted and dashed lines when the CMB is assumed to be ideal or highly contaminated by foreground emission (e.g., SZ clusters), respectively. Note that the dotted and dashed lines may be overplotted in some cases. When not visible at all, those lines are mixed to the solid line case.