File:Stafford Air & Space Museum, Weatherford, OK, US (09).jpg

English: The emergency oxygen mask of Thomas P. Stafford, commander of the Apollo crew on the Apollo–Soyuz Test Project. Stafford and his two fellow crewmembers, Vance D. Brand and Deke Slayton, were forced to use these masks just after the splashdown of their Command Module capsule, and the masks probably saved their lives. During re-entry, as the capsule fell through the lower atmosphere before deploying its parachutes, the crew, as part of their checklist, was supposed to arm the capsule's Earth Landing System (ELS) at 30,000 feet (9,144 m) altitude, but they missed doing so, possibly due to noise in the cabin. The ELS would have automatically jettisoned the capsule's apex cover and deployed its drogue parachutes at 24,000 feet (7,315 m); when the crew didn't see this happen, they performed these actions manually. The manual deployment of the drogue chutes started the capsule swaying. Since the ELS was not armed, the capsule automatically fired its reaction control system thrusters to counteract the swaying. By this time the cabin pressure relief valve had opened to equalize cabin pressure with the outside air, and this valve now sucked nearby thruster exhaust into the cabin, where this exhaust, which included toxic unburned propellants (monomethylhydrazine and dinitrogen tetroxide), began to irritate the astronauts. Soon after, they realized their oversight and armed the ELS, which automatically shut off the thrusters. Despite the poisoned atmosphere, which had the astronauts coughing increasingly badly, they had to focus on the remaining re-entry tasks until splashdown, which came hard enough to flip the capsule over. Inside the upside-down capsule and fighting hypoxia, Stafford had to release himself from his harness and crawl to get the oxygen masks for the rest of the crew. Vance Brand passed out and Stafford had to help him with his mask. Once the crew had recovered a bit, they first activated the capsule's uprighting system to bring it right side up and then opened its vent valve to clear the contaminated air. Their exposure to the gases caused them to develop pneumonia-like symptoms, and they had to spend two weeks in hospital to fully recover from the effects.

Displayed at the Stafford Air & Space Museum, Weatherford, Oklahoma, U.S. The museum was named for Stafford, a native of Weatherford.