An overpressure protection system and method for a hyperbaric chamber having a secondary relief valve in pressure communication with a hyperbaric chamber and configured to actuate upon occurrence of a predetermined pressure condition. Actuation of the secondary relief valve causes an output signal to be delivered to a relay input, which results in actuation of an emergency vent valve to close an oxygen shutoff valve to terminate the flow of oxygen to the chamber. In the preferred embodiment, the predetermined pressure condition occurs when the chamber pressure exceeds the maximum chamber set point plus a predetermined pressure differential. In the preferred embodiment, the relay may be pneumatic or electromechanical.
