smooth transition eddies and turbulents which may have been created at the edge 56 of the embodiments shown in fig2 and 3 are reduced thereby further reducing depositing of particulates at the inlet 36 turning to fig1 c and 6a the manner by which separation occurs according to the prior art will now be described the gas stream upon entering the separator 12 begins to swirl downwards as induced by the flow directing surface 42 the gas stream then begins to accelerate as the stream spirals downwardly in the cone section of the separator it has been found that where most efficient separation takes place a certain amount of the gas stream bypasses this most efficient region of the vortex flow pattern and enters directly into the finder tube 40 this bypassing flow carries with it particulates which were not removed by the separation and must otherwise be accounted for to prevent such bypassing of flow the cyclone separator 12 in conjunction with either the duct 68 of fig2 4 or 68 39 of fig5 may include a flow directing surface 42 39 as shown in fig5 and 6b the surface 42 39 is disposed in the annular swirl chamber 52 for the separator 12 and has a first portion 74 arranged to extend horizontally from the.