Flexicon Product and Solutions Guide

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TECHNICAL DATA
Low Fire Hazard (LFH) Performance
LFH encompasses LSF (low smoke and fume) and LS0H (low smoke zero halogen)
Low Fire Hazard (LFH) conduit systems are becoming an increasing part of the specification
in many cabling applications. Public buildings, high rise office blocks, hospital theatres and
transport installations - these are just a few of the instances where Low Fire Hazard products
may be required.
• Highly Flame Retardant to prevent a fire starting or
limit its development if one does start.
• Low Smoke emission in the event of a fire to enable
personnel to see their way to escape.
• Low Toxicity in the event of a fire to ensure personnel
are not overcome during their escape.
• Halogen Free gives an indication of low smoke and
low toxicity. It also rules out halogen acid gas emission
- a fact that is of interest to insurers as acid smoke can
destroy computer equipment and damage the structure
of a building. Halogens are Fluorine, Chlorine, Bromine
and Iodine.
Methods of Assessing Fire Performance
Halogen Free The Halogens are fluorine,
chlorine, bromine and iodine. Chlorine is the
most common in PVC, fluorine is in fluoro-
polymers and bromine appears in flame
retardants. All of them give off highly toxic
fumes and thick smoke. A material cannot be
considered as Low Fire Hazard if it contains halogen.
However a halogen free material is not necessarily Low Fire
hazard as it may not be low toxicity, low smoke and highly
flame retardant.
Halogen content is assessed by various chemical tests and
analytical techniques.
Flame Retardancy The minimum
requirement is self-extinguishing according to
the worldwide conduit system standard BS EN
IEC 61386 where a vertical sample of conduit is
exposed to a 1kW burner and must extinguish
within 30 seconds of the removal of the flame.
The char must not have travelled more than a
certain distance up the sample and there must
be no flaming droplets. Fittings are tested by
means of a 750°C glow wire test.
To assess how flame retardant a material is, the
normal test method is to measure the Limiting
Oxygen Index (LOI) according to BS EN ISO
4589-2 which determines the percentage of oxygen that
needs to be present to support combustion. The higher the
LOI percentage, the greater the flame retardancy of the
material. Oxygen present in normal air is approx. 21%.
Another method is the glow wire test, BS EN IEC 60695-2,
which applies a glow wire to a plaque of material at 750°C,
850°C or 960°C.
UL94 is an Underwriters Laboratories standard that measures
the rate of burning up a vertical test plaque, category V0 is the
most flame retardant followed by V1 and V2. There is a
category HB but this indicates that the material is flammable
even along a horizontal test plaque.
Low Smoke emission There are a number
of fire tests, mainly from the rail industry, where
a specified sample of material is burnt under
controlled conditions in a given size smoke
chamber and the smoke obscuration of a defined beam of
light is measured. Although the different tests are similar, the
results and the requirements are different.
Low Toxicity There are a number of fire
tests, mainly from the rail industry, where a
specified sample of material is burnt under
controlled conditions in a given size smoke
chamber and the fumes are analysed for
various gases, the concentration of each gas is
then multiplied by its toxic potency to give a toxicity index.
Although the different tests are similar, the results and the
requirements are different.
If halogens, sulphur or phosphorus are present in a material,
it is unlikely to pass the low toxicity tests.
Low Fire Hazard systems are required to protect personnel and property in the event of a fire and may be demanded by
specifiers, occupiers, building owners, fire services or even insurers.
At Flexicon we define a Low Fire Hazard product by having all of the following properties: