Cleaning of a Flag 4 (top) and a Flag2 (bottom) VIPERS spectrum. For each panel: the upper plot is the observed (sky subtracted) spectrum (thick black), superposed to the mask (straight red lines) and the rescaled sky residuals spectrum (thin cyan); the middle plot shows the automatic cleaning, with the expected position of the [OII], Hβ and [OIII] lines marked in black by the dash-dotted lines; and the bottom plot is the manually edited spectrum.