Hydrogen isotopes are separated from other gases by permeation through palladium and palladium-silver alloy diffusers, or permeators, in the Tritium Facilities at the US Department of Energy Savannah River Site (SRS). Diffusers have provided effective service for almost 40 years. This paper is an overview of the operational experience with the various diffuser types that have been employed at SRS. Alternative technologies being developed at SRS for purifying hydrogen isotopes are also discussed.