A method of two-fold separating dust from dust-laden suction air

A method for separating dust from dust-laden suction air comprising the steps of: - introducing dust-laden suction air through a vacuum intake (4) into a separation chamber (5) so that the suction air flows in a spiral path in rotation in a first transport direction (13); - ejection of a portion of the first dust suction air through a first dust discharge opening (10) of the separating chamber (5); - reversing the suction air flow from the helical path of the first transport direction (13) on a helical track of a second transport direction (14), which is opposite to the first transport direction (13) substantially; - after which the suction air after reversal of the first (13) in the second transport direction (14) is introduced at a dip tube inlet in a dip tube (15), the double or multi-walled with one or more inner pipes (20) and an outer tube (19 ), which is the or the inner tubes (20) at least partially wrapped, is formed; and - ejecting a second dust fraction of the suction air through a second dust discharge port (16), which is formed by at least one aperture in the dip tube (15) which is designed as a window or slot in an inner tube (20) of the dip tube (15) during the, suction air rotating in the second transport direction (14) flows.