Top: dust emission per N_HI at 857GHz versus the 3000/857 GHz (100/350μm) ratio. Local (black), IVC (blue – dot is IV Arch, triangle IV/LLIV Arch, square Complex K), residual (green). Solid line is the DustEM model for the diffuse ISM (Compiègne et al. 2011), with radiation field variations from G = 0.1 to G = 5. Dashed line is the same model but with a relative abundance of VSGs four times higher than the standard diffuse ISM value. Dotted lines gives the local ISM fiducial values (G = 1.0). Typical uncertainties are shown for each Hi component. Bottom: 5000/857 GHz (60/350μm) ratio as a function of the 3000/857 GHz (100/350μm) ratio.