A hollow fiber membrane gas separation apparatus of a compact design suitable for separation and purification of gases is disclosed. The apparatus comprises an outer housing that consists of a detachable bowl and a head closure, and a removable hollow fiber membrane cartridge positioned therein. The cartridge contains several concentric separation zones and provides for efficient countercurrent flow configuration between the feed gas on the shell side and the permeate sweep gas on the lumen side of the hollow fiber membranes.