Abstract: A one-shot pressure relief device which can be hermetically sealed comprising a housing with a port fitting for connecting to a pressure zone to be monitored, the fitting having a passage which leads into a central cavity within the housing from the top side. The cavity is divided and sealed into two portions by a thin metallic membrane fixedly mounted adjacent a snap-acting pressure disc member with a central aperture. A hollow puncture member is positioned in the bottom of the housing in axial registry with the center aperture of the snap-acting pressure disc so that upon an over pressure condition in the monitored zone, the disc will snap over center at a predetermined condition allowing the membrane to move likewise piercing itself on the puncture member thereby venting and relieving the over pressure condition.