Technical Concepts
The intumescent resins in batt-based firestop pillows contains hydrates, or chemically bound water. On the fire side, the plastic bag burns off exposing the intumescent to the fire, which releases the water in the form of vapour or steam. The steam rises and hits the plastic bag interior on the unexposed side, where it condenses back to water, and runs back down to cool the installation below. Batt-based pillows are held in place by compressing them, allowing friction to restrain them. If replaced a suffieint number of times, the pillows will retain a permanent compression, requiring their replacement with new components.
For the fabric bag based pillows, the vermiculite, the fabric bag and the graphite are noncombustible. The graphite expands but forms no bond with anything around it, unlike the resin-based instumescents. There is also no significant release of chemically bound water. Usually the bags are not entirely filled and cannot be significantly compressed, requiring mesh or grid installations to stay in place.
The Fomox-based pillows intumesce.
Read more about this topic: Firestop Pillow
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