Abstract: Equipment in an enclosure is shielded from affecting, or being affected by, external electromagnetic and magnetic fields. A flooring within the enclosure includes first and second portions. The first portion supports the enclosure walls and provides electromagnetic and magnetic shielding. The second portion is paramagnetic and is disposed inwardly of, and spaced from, the first portion. A third flooring portion disposed between the first and second portions and expansible with heat provides a compatible coupling with the first and second portions. A door in a wall aperture is movable between opened and closed positions. Resilient fingers on the door co-operate with the door jambs to provide an electromagnetic coupling between the door and the walls when the door is closed. A window in another wall aperture provides for a visual inspection of the enclosure and for electromagnetic coupling with the walls.