A Definitive Guide to LSZH Low-Smoke Zero Halogen Cables
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A Low-Smoke Zero Halogen (known shortly as LSZH or LSOH) cable is a cable with insulation and/or jacket that minimizes the smoke and produces no halogen when exposed to heat sources and fire.
Read this blog to learn where these cables are used, their properties, and how they radically differ from PVC and LSF.
An LSZH cable is useful for environments where fire and high temperatures might be hazardous and smoke and toxic fumes risk public safety, such as industrial plants, public buildings, and vehicles. LSZH cables are intended for indoor use.
Low-smoke zero halogen cables emit less than 0.5% hydrogen chloride gas and smoke when burnt.
As power and control cables in public buildings: airports, bus stations, railway stations, shopping malls, state buildings, hospitals, schools, and universities.
In data centers
In industrial buildings
In aircraft and ships
Any type of construction that is difficult to escape if a fire happens
In any other setting where regular cables are used
LSZH cables are flame-retardant
LSZH cables produce no halogens during the fire, making them less toxic for humans and the environment. This makes them different from other types of flame-retardant cables. Exposure to halogens harms the environment and lungs of people and other mammals.
Self-extinguishing jackets of LSZH cables prevent the fire from spreading further.
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LSZH cables are UV resistant
These cables are water-resistant but not waterproof, except for specific variations used on the board of the ship.
A standard PVC cable can be flame-retardant or not flame-retardant, but they produce harmful black smoke during the fire and release harmful chemicals, including halogen. In many instances, the smoke and gasses produced during a fire cause more harm to people than the fire itself. For this reason, a flame-retardant PVC cable does not really protect people in case of fire.
PVC cables are a great way to save costs, but it is not worth it for commercial and public buildings where safety is a great concern.
The cons of LSZH cables compared to PVC is that they are less flexible and more expensive, but these are negligible if you take into consideration the damage to people and property that a large-scale fire causes.
Low-smoke zero-halogen &#;able is often compared to LSF Low Smoke and Fume cable because the names sound very similar. The relative lack of standardization and naming regulation is the driving factor behind such confusion. In reality, LSZH and LSF cables do not have anything in common.
LSF cables are altered PVC cables that produce less harmful gasses and smoke when burning than traditional PVC. However, the material of LSF cables is still PVC, so gasses are emitted nevertheless, there are just 5x less of them. So, LSF cables are slightly improved compared to PVC, but they have no qualities of low-smoke zero-halogen cables, so they should not be bought in place of LSZH cables.
Confusing LSZH and LSF cables can actually be dangerous if the intention is to place LSZH cables to protect the building from fire.
NNC offers a wide range of low-smoke zero halogen cables of high quality at excellent prices, including:
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 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%.
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 stipulates that emissions of HCl by LSZH cables must not exceed 0.5%.
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.
As a leading rail & metro cable supplier, Eland 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.
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