A canned or sleeved rotary machine is equipped with a rotor (101) in contact with a particle-laden, acidic or corrosive gaseous atmosphere, and with a functional electrical assembly such as a magnetic bearing comprising a rotor armature (106) secured to the rotor (101) and placed in the gaseous atmosphere and a stator armature (104) secured to a stationary support (102) and positioned facing the rotor armature (106), the stator armature (104) comprising at least one winding (142, 143) and a ferromagnetic body (141) which are positioned in a protective metal enclosure comprising a solid part secured to the stationary support (102) or coincident therewith, a thin can or sleeve (103) and a hermetic passage (108) for wiring (108a) supplying the windings (142, 143). A potting compound (107) fills residual internal gaps left in the ferromagnetic body (141), the windings (142, 143) and the wiring (108a), and a dead volume (109) in which the pressure is below atmospheric pressure is created inside the protective metal enclosure (102, 103, 108).