These 'fire stop systems' incorporate an intumescent compound, usually based on melamine. Upon heating above a critical temperature, the compound expands, without sagging and produces a foamed-char product, based on carbon, when ignition temperatures pertain. This foam-char then acts as a heat shield, a smoke and fume seal and a gap-filler, replacing burned or melted components like wire insulation or pvc conduit. But only for a limited period. That's because eventually the carbonised char burns through. Hopefully, the delay in smoke and heat propagation gives occupants time to escape a fire.
Alan
ps. I might add that steel conduits might need to have an intumescent seal on their inside diameters where they penetrate a wall or floor in certain arrangements, as they could conduct combustion products or fire.
[This message has been edited by Alan Belson (edited 04-05-2006).]
