Robin Laing wrote: > Tim wrote: >> On Tue, 2006-04-04 at 10:26 -0600, Robin Laing wrote: >> >>> In our city, plenum rated cables have to be used in anything that has >>> any type of air access. If you bring the cables out in any way to a >>> patch panel, they have to be plenum rated. >> >> >> In one sense, that does sound a bit silly. I mean, is the equipment the >> cables run into also made out of similarly fire retardent, and non-toxic >> fume generating, plastic? >> > > But in many cases, don't some rules seem silly? > > The issue as I see it, if there is a fire, the cable cannot be a method > of transferring the fire into the walls via the insulation. In case a > cable ends up having to run in a drop ceiling or there is a construction > change down the road. All the cables are the same standard. > No - the reason for plenum rated cable it that standard thermoplastic insulation gives off toxic fumes when it burns. If it is in an air plenum, the air flow spreads the fumes to areas that the fire has not reached yet. I sometimes wonder about that, because you are also going to be moving toxic fumes from the room's contents until the fire dampers close, or the fire alarm shuts down the fan, but who am I to say... The standard thermoplastic insulation is not that much better at transferring fire then the Teflon coated plenum cable. Unless you have a lot of heat, thermoplastic tends to smolder, and not sustain a flame. Mikkel -- Do not meddle in the affairs of dragons, for thou art crunchy and taste good with Ketchup!
