Flux distribution of 500 μm-risers from this work (coloured blue area) compared to 500 μm-risers considered for a submillimetre interferometric follow-up in different studies. Orange, black, and green stepfilled lines represent sub-samples selected from Ivison et al. (2016), Asboth et al. (2016), and Dowell et al. (2014), respectively. Flux distribution of red sources from the B17 that are modelled applying the same selection criteria presented in this work is represented by the dashed red line.