PURPOSE: To avoid the need for a DC-AC adapter system by arranging an oxygen concentrator within the foot rest cavity of an automobile so that the air flowing in this device is passed from the side part to the side part of the automobile.

CONSTITUTION: This portable low profile DC oxygen concentrator is required to hold molecular sieve materials 40 immobile. The molecular sieve materials 40 break slightly during use. Compression occurs next and eventually the length of a spring loaded bed 32 shortens. This tendency increases further as the device is portably used in a vehicle. The molecular sieve materials need be so held as to accept this shortening and to hold the bed 32 immobile in spite of the generation of the fine materials by breakage. While the bed of the fine material is housed, the bed 32 is so held as not to move. Such holding is mainly achieved by a moving piston assembly 54 and more particularly by filter paper 78.