Hydrogen was produced by dark fermentation in this work and the gaseous mixture-containing H-2, CO2 and N-2-was separated by a two-step gas separation system, where porous and non-porous membranes were used. Calculated (modelling) and experimental data using two-compound gases were compared and it was found that the model curves fitted well onto the measured ones. Moreover, results of the integrated system were presented, where biohydrogen was recovered and enriched in the gas stream.