Air-separation device, inerting device and aircraft comprising such a device

An inerting device for an aircraft tank comprising an air separation device, said air separation device comprising:

• a casing having a generally cylindrical form and a longitudinal axis and having an air inlet orifice and a purified gas outlet orifice at first and second ends thereof, respectively;
• a filtration element enclosed within said casing, said filtration element comprising a bundle of hollow oblong fibers forming a membrane, a longitudinal axis of the fibers being parallel to said longitudinal axis of said cylindrical casing, said bundle having, at at least one end thereof, a rigid layer of a material;
• a first retention unit supported on said rigid layer and being adapted and configured to retain said bundle of fibers in said casing, said first retention unit comprising at least one spring unit arranged inside said casing, each of said at least one spring unit of said first retention unit being compressed between a first longitudinal end of the bundle of fibers and a first stop that is formed by said casing so as to permit expansion or contraction of said bundle of fibers.