Thermoformed intake duct (1) made of non-woven material and including flanges (6, 7, 8, 9) parallel to the longitudinal axis of the duct, projecting from the outer surface of the duct, a first portion (4) of the duct being formed in the form of a first bellows, a first bellows-shaped portion (4) having two longitudinal flanges (6, 7) diametrically opposed along a first diameter (D2), characterized in that the duct includes at least a second bellows-shaped portion (5) having two longitudinal flanges (8, 9) diametrically opposed along a second diameter (D3) of the duct which makes, with respect to the first diameter (D2) of the two flanges (6, 7) of the first bellows-shaped portion, a non-zero angle, and especially 90°.