This fan (1) includes a volute (2) whose inlet opening (3) is in communication with the oxygen feed line, an impeller (4) situated immediately downstream of the inlet opening of the volute and including an inlet opening connected to this inlet opening (3) of the volute and outlet orifices (4a) emerging into the volute (2), and an electric motor (5) for rotating the impeller (4). The fan (1) includes: —a compartment (6) in which the motor (5) and, where appropriate, other electric elements or components belonging to the fan (1) are placed, this compartment (6) including an end wall (13) traversed by the shaft of the motor (5) and being supplied with pressurized air, and—a leak collection chamber (7) situated intermediately between the volute (2) and the compartment (6), this chamber likewise being traversed by the shaft of the motor (5) and including a discharge orifice (20).