shown in Viero et al. (2013a) to be negligible. Fig. \[fig:hershelms\_sky\] shows the three-colour SPIRE images of the HeRS and HeLMS regions. We can clearly see white foreground clouds of Galactic cirrus emission, which have been shown to correlate with HI emission from GASS 21-cm data in Viero et al. (2013b).

In this paper, we also include SPIRE maps of a subset of the HerMES level 5 and level 6 fields[^6], which have significant overlaps with our SDSS quasar samples. In particular, the HerMES Boötes field (11.3 deg$^2$) and the Lockman-SWIRE field (15.2 deg$^2$) overlap with the SDSS DR7 QSO sample. The Boötes field and the [*XMM*]{}-LSS field (21.6 deg$^2$) overlap with the SDSS DR9 QSO sample. Fig. \[fig:lss14\_sky\] shows the three-colour SPIRE images of the Boötes, Lockman-SWIRE and [*XMM*]{}-LSS field. Out of these three fields, the [*XMM*]{}-LSS field is the most contaminated by cirrus emission, but all three fields have significantly less cirrus contamination than the HeRS or HeLMS field. In addition, the level 5 and 6 fields are significantly deeper than HeRS or HeLMS. The 5-$\sigma$ noise level in the [*XMM*]{}-LSS and Boötes field is 25.8, 21.2 and 30.8 mJy at 250, 350 and 500 $\micron$, respectively. The 