For the purposes of the ASTM E 2307 test standard, the interior face
of the exterior wall is at the interior surface of the wall’s framework.
Therefore, the test is not intended to evaluate the spread of fire within
the core or cavity of the exterior wall assembly. Nor is it intended to
evaluate the passage of flames via the openings in the exterior wall
(i.e. leap-frogging), which is addressed by Section 705.8.5. Most
of the tested and listed systems will involve details and information
regarding the need for spandrel insulation or finishes to protect
the interior of the curtain wall, which appears to create quasi-
fire-resistance-rated walls. But this is not the case. The spandrel
insulation is used to provide some integrity to the exterior curtain
wall, keeping it intact enough to allow the safing material installed
in the void to remain in place. (See details B and C in Figure 5.5 to
see the distinction between the voids addressed by ASTM E 2307.)
If the insulation or finish on the inside face of the exterior wall is not
adequate to resist the test’s fire exposure, then the exterior wall will
deteriorate to the point that it is not able to hold the safing material
in place. Under either scenario, the fire barrier will have failed to
stop the fire from spreading to the upper floor through the void at the
edge of the floor. Perimeter fire containment systems listed using
ASTM E 2307 typically include:
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Some types of mineral wool insulation mechanically secured to the
interior side of the spandrel panels of the exterior wall to protect the
curtain wall framing system.
A reinforcing angle or channel mechanically secured to the curtain
wall adjacent to the floor slab.
Compressed mineral wool insulation filling the gap or void between
the floor and the curtain wall, which is commonly referred to as
“safing.”
A smoke seal applied on top of the safing insulation.
Figure 5.7 shows the typical components specified in listings of
tested perimeter fire containment systems.