Abstract: A cyclone separator for separating fine particles or dust from a gas stream comprising a main separator chamber 11 having a tangential gas inlet 10 to form a circulating gas vortex about an axis 12, and a gas outlet opening 19 aligned with the vortex axis at one end of the chamber and communicating with a main gas outlet duct 20. Within the main separator chamber 11 there are positioned baffles or vanes 14,15 which separate off the heavier solid particles into a hopper 13 below the chamber. Adjacent the outlet aperture 19 is an annular opening 21 which communicates with a subsidiary casing 22 having a tangential outlet 23. Fine particles are therefore flung outwards by centrifugal force into the casing 22 and are then separated in a further cyclone separator 25.