The high-pressure flow cell is designed to test the diffusivity and permeability of gases—particularly H₂, CO₂, and CH₄—through porous media at elevated pressures and temperatures of up to 35 MPa and 150 °C, respectively. Furthermore, the capillary breakthrough pressure of gases in water-saturated porous media can be determined. The flow cell is equipped with a sapphire window and an endoscopic camera to facilitate the visualization of gas permeation through the water-filled pores at breakthrough. An inline Raman spectrometer is used to record changes in gas mixture compositions. The integrity of completion and sealing systems for hydrogen and carbon dioxide storage is the main focus of the studies being conducted. The setup includes high-precision pressure transducers on the upstream and downstream sides. The setup is housed in an environment that is certified for working with compressed hydrogen.