Systems and methods for selectively extracting hydrogen gas dissolved in oil are provided. In one embodiment, a system includes a selectively permeable membrane provided at a point of contact between oil and a sensor chamber. The selectively permeable membrane has a hydrogen specificity and a thickness selected to minimize detection of further gasses dissolved in the oil by a hydrogen gas sensor cross-sensitive to the further gasses. The selectively permeable membrane can include polyimide. The further gasses include carbon monoxide, acetylene, and ethylene. The system can include a further membrane and a porous metal disc. The porous metal disc is bound to the selectively permeable membrane by using the further membrane as an adhesive layer and by applying pressure and temperature. The porous metal disc supports the selectively permeable membrane and the further membrane against pressure of the oil when exposed to a vacuum. The further membrane includes fluorohydrocarbons.