A gas assisted re-breathing device is provided for life support of individuals venturing into harsh environments, particularly the underwater environment, which results in reduced work of breathing. In the pressurized gas assisted re-breathing device, pressurized gas, actuated by the breathing pressure local to the mouthpiece, acts to move a flexible gas storage container on behalf of the individual and a loop seal valve is forcibly shut during assisted breathing, which seals the assisted breathing loop to prevent premature venting of breathing gas to the surrounding environment, unless the assisted breathing loop is full, whereupon the loop seal valve opens to allow excess breathing gas to escape into the surrounding environment through forcible exhalation by the individual through one or more conventional one way valves that prevent backflow from the surrounding environment back into the loop.