However, these can be further categorized and understood by the
following chart:
How firestop systems perform their functions will depend on the
types of materials used and the intended purpose of the system.
The systems will perform their required functions as a result of the
fire-resistive properties of the materials in combination with their
proper installation. These systems can then prevent the passage of
flames or increased temperatures through the penetrations of the
fire-resistance-rated assembly. In a June 2007 publication, Best
Practice Guide on Fire Stops and Fire Blocks and Their Impact on
Sound Transmission, the National Research Council of Canada’s
Institute for Research in Construction provided a nice summary in-
dicating firestop materials possess one or more of the following
properties:
INTUMESCENCE
The property of a material to increase in volume upon exposure to
heat. This action causes the firestop to fill the opening, thus cre-
ating a seal in a fire separation. Typical intumescent products be-
gin to swell in the range of 300 to 355°F (150 to 180°C), & reach
full expansion in the range of 660 to 750°F (350 to 400°C) before
hardening into a rigid material. The rigid char layer, formed towards
the end of the intumescence reaction, insulates and prevents flame
passage through the penetration.
Some intumescent material formulations will also cause significant
pressure while expanding. This pressure can be useful in applica-
tions such as the firestopping of plastic pipes, where the pressure, if
suitably directed, can compress and seal the softening pipe during
a fire. Other intumescent formulations provide minimal pressure
while expanding, which would make their selection and application
appropriate for applications where pressure is not useful or critical.
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