Abstract: An external middle joint for an extraction arm has one first half and a second half, an inner tube and an outer tube, the inner tube being connected to a fan mounted on a wall, the outer tube having an extraction hood. The first half is connected to the outer end of the inner tube and the second half is connected to the inner end of the outer tube. Each half has a connecting piece connecting the first half to the outer end of the inner tube and connecting the second half to the inner end of the outer tube. A length of hose interconnects the outer end of the inner tube and the inner end of the outer tube, so that a continuous channel is formed from the fan to the extraction hood. Each half has two legs extending on either side of the hose, each leg being articulated to the corresponding leg of the opposite joint half by means of bolt connections. The latter have a bolt which is non-rotationally mounted in one of the legs of the other joint half and which support a knob.