A system and a method for providing a secondary source of breathing gas to a mask are disclosed. The system includes secondary reservoir having a breathing gas, the secondary reservoir connected to a primary line by a secondary line. A pressure switch detects a pressure in the primary line and, upon a pressure lower than a threshold, actuates an actuator to permit the flow of breathing gas from the secondary reservoir through the secondary line. A valve may be configured to prevent a flow of gas from the secondary line to a source side of the primary line. The method includes detecting gas pressure and actuating an actuator upon a low gas pressure to permit a flow of secondary gas to the breathing mask by way of a secondary line. The gas may be prevented from flowing from the secondary line to a source side of the primary line.