Filtering efficiency of dust of 1 micron to 100 meters by a MMSN planetesimal belt with planetesimals of 1 to 10 000 km in radius extending from 0.1 to 35 AU for a turbulent parameter α = 10^-2 and assuming monodisperse size distributions for planetesimals and dust grains. Top panel: contours of the disk-integrated filtering factor X_filter. Bottom panel: orbital distance at which X_filter(r) = 1 for dust particles drifting in from beyond 35 AU. (The integration thus starts from 35 AU and goes inwards.)