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With regard to your question:
Actually, any cable jacket that you may use indoors shell be made of fire
retardant materials for the sole reason - you bring lots of polymer resins -
highly combustible materials - into the place, which is not suppose to be a
fireplace. That's why there is a 15 meters limitation for OSP cable
placement within a building. Polyethylene (usual outer sheath material for
OSP cables) is not considered fire retardant at all, because it burns like
an oil (emitting pretty the same amount of energy).
PVC composites are known as producing not as much heat as Polyethylene and
maybe even more important - having slower flame spread, that gives people
more time to escape a fire. In an office environment (the type of
environment, where structured cabling is usually installed) PVC composites
are most often used as outer jacket materials. Composites means that some
ballast mineral materials added to slow down a flame spread. So they are
"fire retardant" in comparison to Polyethylene, but still they burn and
produce pretty much heat. That's why it is dangerous to use this PVC
composites is such a spaces, where may be a presence of some air movement,
because fresh oxygen will diminish all the "fire retardancy" efforts and
fire will spread fast again. Such a spaces, whatever their primary purpose
is, called "plenum(s)". HVAC tunnels, above-the-ceiling spaces, any other
cavity, that may create a return path for conditioned air, are good examples
of plenum spaces. In this case special jacket materials are used and cable
is called "plenum rated". Teflon FEP is the most well known plenum rated
cable jacket material. Its what DuPont called "Low fuel-load fluoropolymer".
In few words its the material that produces 30 times less energy than
Polyethylene while burning, and gives zero flame spread.
For the identification purposes NEC in Article 800-51 sets listing requirements for
communications wires and cables, where
All cables are for communications use and
CMP is plenum cable
CM and CMG -general purpose
So look at a cable mark and you'll be able to say that some particular cable
is suitable for some particular installation. And one very small remark.
There is no big difference between CM and CMR cables, they are all
PVC-based, but riser cables have more of those ballast materials to even
more slow flame spread down. You may check it yourself. Try to burn CM cable
while horizontal. It should burn only above a naked flame of your lighter.
Rotate cable 90 degrees - and flame will move up (and quickly if the cable
isn't that good) because of convection. Ideally, you shouldn't see this
flame moving up with riser rated CMR cable.
There is DuPont site on the Internet located at
contains many interesting facts about cables and fires.
And you are always welcome to see updates at our site