it should not here lead to any deterioration in the exhaust gas composition nor to the overloading of any catalyzer which may be present for this reason the signal generated by a lambda sensor accommodated in the exhaust system of the vehicle and therefore not represented also makes its way to the control unit 28 which by suitable commanding of the second valve 46 ensures an emission optimal progression of the filter regeneration to this end the second valve 46 is controllable that is to say that the current supplied to the second magnetic coil 58 via the line 30 is metered or modulated or cycled in such a way that the closing body 48 acts as a control valve by which the air current running out of the third line 26 through the activated carbon 24 and via the second line 25 to the internal combustion engine is regulated in fig6 the two way valve unit 23 has tacked on to it a further pressure equalizing valve unit 80 this creates a bypass and could also be separate from the valve unit 23 and connected thereto by lines it has the purpose of preventing both the creation of an overpressure and the creation of an underpressure in the tank 1 in its housing 81 two flow paths are respectively operated by an automatic valve a first valve chamber 82 is connected on the one hand to the first line 22 and thus to the inside of the tank 1 and on the other hand via openings 83 to the interior 85 of the two way valve unit 23 the openings 83 can be covered by an elastic valve plate 84 when on the side.