A cooling apparatus includes a chamber and a pressure-relief element. The chamber includes a coolant in a liquid phase disposed near a heat-generation object. The coolant in the liquid phase dissipates heat from the heat-generation object and is converted from the liquid phase to a vapor phase upon the coolant in the liquid phase reaching a boiling temperature. The pressure-relief element has a conduit. A first end of the conduit is submerged in the coolant in the liquid phase internal to the chamber and a second end of the conduit is connected to atmosphere external to the chamber.