A preservation assembly of a PEFC stack which is capable of sufficiently inhibiting degradation of performance of the PEFC stack particularly during a time period that elapses from when the stack is placed in the uninstalled state until it is placed in the installation position and is practically used. The PEFC stack is provided with an oxidizing agent passage having an inlet and an outlet and extending through a cathode and a reducing agent passage having an inlet and an outlet and extending through an anode. The PEFC stack is preserved in an uninstalled state in such a manner that an interior of the oxidizing agent passage and an interior of the reducing agent passage are set in a pressure-reduced state.
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