Webb said the risk of fire in the 012 command module had been greater than recognized when procedures were established for the January 27 manned test that had ended in a fatal flash fire. Successful Mercury and Gemini flight experience with pure oxygen atmospheres and the difficulty of keeping dropped items out of complex wiring and equipment had led to placing Velcro pads, covers over wire bundles, and nylon netting in the CM cabin. Although mostly of low combustion material, they were not arranged to provide barriers to the spread of fire. Soldered joints also had melted, and leaked oxygen and fluids had contributed to the fire. The capsule rupture caused flames to rush over and around astronaut couches to the break, preventing the crew from opening the hatch. And the environmental control unit would require careful examination and possible redesign.
Seamans reported an electrical malfunction was the most likely source of ignition of the fire, which apparently had three distinct phases. Principal preliminary recommendations of the Review Board were:
- Combustible material in the CM should be replaced whenever possible by nonflammable materials, all nonmetallic materials should be arranged to maintain fire breaks, oxygen or combustible liquid systems should be made fire resistant, and full flammability tests should be conducted with a mockup of each new configuration.
- A more rapidly and more easily operated CM hatch should be designed.
- On-the-pad emergency procedures should be revised to recognize the possibility of cabin fire.
The Board also suggested some subsystems and procedures could be improved for safety. It did not recommend that cabin atmosphere for operations in space be changed from pure oxygen at pressure of 3.5 newtons per square centimeter (5 pounds per square inch), but did recommend that tradeoffs between one-gas and two-gas atmospheres be reevaluated and that pressurized oxygen no longer be used in prelaunch operations.