Abstract: An emergency breathing device comprises: a mouthpiece; a valve body having one end receiving a hose coupling and one end receiving the mouthpiece, the valve body having a valve opening adjacent the mouthpiece end; a resilient seal interiorly of the valve opening; a valve having a seal engaging surface, gas pressure in the hose urging the valve into a sealing engagement with the seal; and, a valve actuator extending through the valve opening and substantially through the mouthpiece. Inward squeezing pressure exerted on the valve actuator through the mouthpiece opens the sealing engagement, allowing a breathable gas to flow from the hose into the mouthpiece. The device can be particularly adapted to be responsive to biting pressure while held in a diver's mouth and to operate right side up and upside down.