(Fig 5.3)
Several phrases have been coined for the systems that protect
the void at the intersection of a fire-resistance-rated floor and an
exterior curtain wall. Some of the designations are perimeter fire
containment systems, perimeter joint systems, floor edge joint
systems, safing joint systems and perimeter fire barrier systems.
The phrase “perimeter firestop systems” describes the situation
well. The systems occur at the perimeter of the building. The intent
of the systems is fire containment. The curtain wall is typically not
fire-resistance rated, so these systems should not be confused with
joint systems evaluated to ASTM E 1966 or UL 2079. These systems
include the specific floor construction, the exterior curtain wall, the
protection on the interior face of the curtain wall if provided, and the
material(s) used to protect the void between the floor slab edge and
the curtain wall. The materials used in the void are often referred to
as safing materials.
Code users should also recognize that the intersection of the exterior
wall and the floor assembly provide multiple different paths that may
allow a fire to spread. The code establishes different requirements
for each of these potential paths and addresses means to prevent
the spread of fire through these paths. Conceptually, the easiest
way to look at the three paths for the fire to spread to adjacent floor
levels at the exterior wall are: