Air flow through two argillaceous rock formations is investigated on the basis of laboratory work and its modelling to help in the interpretation of the results. Priority in the experimental program has been given to study the volume change response of these initially water saturated materials along relatively fast and controlled volume rate air injections. These high rates intend to give preference to single-phase air flow mechanisms associated with the opening of stress-dependent pathways. Particular attention has been focused on the changes in the pore network to detect opening of fissures after air injection tests using mercury intrusion porosimetry. Selected experimental results have been simulated using a fully coupled hydro-mechanical finite element code, which incorporates an embedded fracture permeability model to account for the simulation of the gas flow along preferential pathways.