Admittedly, Phillips said, MSC had considered using a freon extinguisher system shortly after the AS-204 accident, but it had been rejected, largely because of toxicity factors and because tests had shown the agent ineffective in extinguishing combustion of polyurethane in a pure oxygen atmosphere. A number of factors now dictated a reevaluation of such an extinguisher system, however:
- Additional testing of late had indicated a lower toxicity problem than earlier believed.
- The addition of oxygen masks to the spacecraft now afforded some protection against a toxic atmosphere.
- Because of post-accident changes inside the cabin, the flammability problem had been reduced to a few specific materials (quite different from polyurethane foam) sited in compartmentalized locations inside the cabin.
- The oxygen-nitrogen mixed gas had been selected as the prelaunch atmosphere inside the cabin.
In view of these changes, Phillips said, a freon extinguishing system might be better than the present jelled water extinguisher (quicker activation and reduced equipment damage). He asked that Low not overlook this potential improvement in crew safety, which could be of particular value during the high-risk period of launch, when the crew was essentially immobilized by the forces of acceleration.