Guangdong Shengyu Cable Industry Co., Ltd. |
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5 Core Fire Retardant Low Smoke Cable Halogen Free Wire BS 6724 Copper Conductor
We supply a comprehensive range of Low Smoke Zero Halogen (LSZH)
cables for use in applications where smoke emission and toxic fumes
could pose a risk to human health and essential equipment in the
event of a fire.
Unlike PVC cables and those made of other compounds which produce
vast amounts of dense black smoke, toxic fumes and acid gas when
exposed to fire, LSZH cables produce very low levels of smoke and
toxic fume and no acid gases. They are therefore often specified
indoors, especially in public areas, and in other hazardous
environments and poorly ventilated areas. This includes cars,
aircraft, railway carriages and ships. LSZH sheathed cables are
commonly used across tunnels and underground rail networks.
The "Low Smoke" element of LSZH cables
According to Part B of The Building Regulations, a leading planning
and building regulations resource for England and Wales:
"The primary danger associated with fire in its early stages is not
flame but the smoke and noxious gases produced by the fire. They
cause most of the casualties and may also obscure the way to escape
routes and exits. Measures designed to provide safe means of escape
must therefore provide appropriate arrangements to limit the rapid
spread of smoke and fumes."
Burning PVC has been found in tests to reduce visibility in the
surrounding area by as much as 50% within 10 minutes. After 30
minutes, visibility can be reduced by as 90% making it
unnecessarily challenging to escape the area.
By comparison, BS EN 61034 specifies a smoke density test,
performed inside a chamber 3m x 3m x 3m. The test is often referred
to as the 3 metre cube test. By monitoring the transmittance
reduction of a white light beam running from one side of the
chamber to the other at a set height, the build-up of smoke inside
the chamber can be measured. For a cable to be classified as low
smoke it will often have a minimum light transmittance of 60%.
The "Zero Halogen" element of LSZH cables
Burning PVC and other cable compounds produce a number of
chemicals, including hydrogen chloride (HCl), which is highly
toxic. Furthermore, when mixed with water, HCl forms hydrochloric
acid; a substance which is both toxic and corrosive. In the case of
PVC, as much as 30% of the emissions can be HCl.
BS EN 60754 stipulates that emissions of HCl by LSZH cables must
not exceed 0.5%.
LSZH vs LSF cables
Whilst there is a common misconception that low smoke and fume
(LSF) cables and LSZH cables are the same, this is not the case and
any confusion between the two could be life-threatening in the
event of a fire.
Unlike LSZH cables, LSF cables are manufactured using PVC
compounds. If they are labelled as low smoke and fume cables it is
due to the manufacturer modifying the compound with various
additive in order to reduce (not eliminate) smoke and HCl
emissions. However, where low smoke zero halogen cables are subject
to strict standards, there are no standards governing LSF cables.
As a result, LSF cables have been found to emit HCl levels in
excess of 20% when burning.
LSZH cable selection
There have been many developments in relation to LSZH cable
standards and legislation since the Kings Cross Station fire of
November 1987 which resulted in 31 fatalities. Findings from the
official investigation outlined that the majority of these deaths
were as a result of toxic fumes, pointing to the vast quantities of
PVC present in the building, much of which was in PVC cables. PVC
cables were subsequently banned by London Underground.
As a leading rail & metro cable supplier, Cables is
well-positioned to understand the implications involved when
selecting an LSZH cable for use in any other industry. Please
contact our technical team to discuss your specific requirements
and our comprehensive range of LSZH cables for all applications,
including building & construction, oil & gas, and marine
& offshore.