A system and method for providing a fuel cell stack purge at fuel cell system shut-down. The method provides a two-stage purge process where the first stage purge uses humidified cathode air to get the fuel cell stack to a known stack hydration level from an unknown stack hydration level at system shut-down. As the stack is purged with the humidified air, the hydration level of the stack decreases asymptotically to the known stack hydration level where the duration of the first stage is set based on the asymptote as a safety margin. Once the known hydration level is achieved, then the second stage purge is performed with dry air to further reduce the stack hydration to a final desired hydration level.
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