Among findings in testing using FAA-approved methodologies were:
The composite materials used for the 787 do not propagate an in-flight fire.
The fuselage skin is an excellent fire barrier, and resists flame penetration far longer than an aluminum fuselage
The toxic gas levels produced in a post-crash fire scenario are similar for both a composite fuselage and an aluminum fuselage
The standards that the FAA has established for the 787 are intended to provide sufficient time for occupants to safely evacuate the airplane following an emergency situation. FAA research shows that the composite fuselage material significantly increases the time it takes for a post crash fire to burn through to the interior, which increases the time for occupants to evacuate before the exterior fire can endanger them.