We receive this question often. The custom material we currently use for the reservoir has a thin film layer of polyethylene plastic laminated to a high tensile strength nylon material. The “air” only comes in contact with the PET thin film side of the material. PET is considered non-reactive even in high oxygen concentration environments.
The materials we use are well researched and also internally tested for potential off-gassing up to 120C. We use a validated GC/MS method to assure we are receiving clean material. While I cannot say we have NO detectable off-gassing, we do have a very small amount ( <4 ug/g, <4 ppm ) at 120 degrees C / 250 degrees F. We estimate that at room temperature ( 25C / 75F ) testing off-gassing would prove to be less than 1ppm. It is as close to zero as we can make it as our best effort to NOT introduce anything other than “pure” air.