This paper represents performance of air-hydrogen free-breathing Fuel Cell (FC) in limited volume conditions. Research work was carried out with thin two-cell stacks related to use in prototype of particular power source system, which includes aluminium-water microgenerator of hydrogen. In small current densities field (<200 mA/cm2) it was established, that after FC had been confined within the small volume, characteristics of FC became better than in non-limited-volume conditions due to self humidification.