Abstract: Gas-filter in the form of an axisymmetric one-part cartridge (1), characterised in that it is essentially constituted by:a) a rigid ring (2) comprising an axisymmetric lateral wall (21) bounded by a flat-forming extremity (23) and by another, fold-down extremity (24), openings (22) being disposed on the wall (21) between the extremities (23) and (24),b) a gas-impermeable backing piece (3) surrounding on the outside the lateral wall (21) of the ring (2) by bearing on the plane extremity (23) of the ring (2) and crimped into the fold-down extremity (24) of the ring (2),c) filter elements (4) disposed between the ring (2) and the backing piece (3).