A bakable, all metal burst diaphragm for low pressure venting is described. The device incorporates a bellows which, under pressure, drives a piece of copper foil into a stationary blade. The spring constant of the bellows allows for a puncturing pressure of 8 psi, while complete rupture occurs at 15 psi. The copper foil can be replaced at minimal cost, and the device can be reliably baked at temperatures up to 300 degrees C.