An electrochemical device which is a novel leaks container for an electrochemical stack, is suitable for working at high absolute pressures. The only parts designed to work at high pressures are the end heads and the leak container. The internal part, the active part, where the reactions using or producing gas take place is designed to operate at low relative pressures. In this way it is possible to build electrolyzers or fuel cells that work at high pressures without the active part of the same being designed for such high pressures.