On January 27, 1967, the crew of Apollo 1 was killed during a routine pre-launch test. A wire arced in the spacecraft, and that spark turned into a raging fire in the pressurized pure oxygen environment. Eighteen months later, the crew of Apollo 7 became the first to fly the revised Apollo spacecraft, but when they removed their helmets in orbit, they did so in a pure oxygen environment. Why, if a pure oxygen environment had claimed the lives of three astronauts already, did NASA not change the cabin environment following the Apollo 1 fire? Well, it did and it didn’t, and the resulting change had as much to do with the Cold War as astronaut safety.