... The Apollo Spacecraft . ... The LM Cabin . ... The Suit Circuit . ... In the Open position, oxygen flowed freely out of the Suit Circuit into the cabin; while, in the Closed position, no flow could occur. ... The fail-safe position was Pull/Egress which closed the valve and prevented the flow of oxygen out of the suit circuit, through the valve, and into the cabin. ... Oxygen flowing out of the Suit Gas Diverter valve returned to the suit circuit through the Cabin Gas Return valve. ...