Abstract: A method and apparatus are provided for preventing contamination of a rotating magnetic disc by particles outgassed from or through the bearings upon which the disc is mounted for rotation. This is accomplished by maintaining a differential pressure aross the bearing nearest the magnetic disc compartment with the higher pressure inside the compartment so that any particles outgassed from the bearing or bearing chamber are constrained to migrate toward a region of lower pressure within the bearing chamber and therefore away from the magnetic disc compartment.