Tubes of ceramic high-temperature proton conductors (CaZr0.9In0.1O3-x, BaZr0.9Y0.1O3-x, and Ba3Ca1.18Nb1.82 O9-x) were used to introduce hydrogen into a vacuum system. A prerequisite was a leak rate below 10(-8) mbar/s for an assembly consisting of the active tube and a 8YSZ support tube. Mass spectrometry showed that the partial pressure of hydrogen in the vacuum system, p(H2), increased linearly with the electric current flowing through the proton conductor. All other important partial pressures remained unaffected by this operation. Calculation of throughput during operation of the hydrogen source essentially revealed that the total current, J, is used to transport protons from the anode to the cathode (t(H) approximate to 1). The number of moles of H-2 transported per second is given by J/2F. In essence, the present proton conductor tube constitutes a precise, current-controllable device, with a response time of a few seconds only, that delivers ultrahigh-purity hydrogen to a vacuum system.