seal assembly are generally ring shaped or radially disposed about a central axis of the seal assembly fig2 illustrates a cross section of one side of a symmetrical seal assembly the seal assembly may be used as the seal assemblies 142 of the centrifugal compressor 100 of fig1 the seal assembly of fig2 includes a primary seal stage 30 and a secondary seal stage 50 the primary seal stage 30 is disposed at an inner or process gas end of the seal assembly 142 the secondary seal stage 50 is disposed at an outer or bearing end of the seal assembly 142 the seal assembly is illustrated in fig2 adjacent to a buffer seal 20 the buffer seal 20 includes segmented carbon rings 21 22 held in a buffer seal housing 24 radial passages in the buffer seal housing 24 provide a purge inlet 15 a secondary vent 17 is disposed between the buffer seal 20 and the secondary seal stage 50 a primary vent 13 is disposed between the primary seal stage 30 and the secondary seal stage 50 a primary inlet 11 is disposed on the process gas end of the primary seal stage 30 when the seal assembly illustrated in fig2 is used in a compressor various gas flows exist during operation in an embodiment filtered process gas 12 flows.