Low Smoke Zero Halogen (LSZH) cables, also commonly referred to as ZHLS, 0HLS or halogen-free flame retardant (HFFR) cables, are manufactured for use in applications where the smoke and toxic fumes associated with PE and PVC cables could be harmful to people or sensitive equipment during a fire.
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A shift in safety regulations across Europe has led to LSZH cables becoming increasingly favoured for specific settings. Let's take a closer look at why this is happening, how these cables work and the standards you need to be aware of when selecting an LSZH cable for your project.
In a fire, a cable&#;s outer sheathing will begin to combust. When exposed to a flame, cables made of PVC compounds will produce vast amounts of dense black smoke, toxic fumes and acid gases. In poorly ventilated or underground spaces where escape routes might be obstructed by smoke, these fumes can become fatal.
LSZH cables are made of a flame retardant outer covering, meaning that their primary decomposition product will absorb the energy from the flame, diluting the fire gases. This causes a charring which acts as a fire barrier, so less smoke and chemicals are released when the cable is burned.
Prompted by several major fire disasters, developments in LSZH legislation have been in motion for many years. The official investigation into the Kings Cross Station fire of confirmed that the majority of the disaster&#;s 31 fatalities were a result of PVC-related toxic fumes. A similar outcome was determined of the Dusseldorf airport fire, in which 27 deaths occurred.
As a result of these incidents, the use of PVC cables has been restricted across several European countries. Ireland, for example, has made the use of LSZH cables mandatory, linking to the Construction Products Regulations (CPR). Meanwhile, countries such as Switzerland, The Netherlands, Germany and Greece have made LSZH a legal requirement in high-risk environments such as evacuation routes and/or high-rise buildings.
Whilst most cable types will now be available with LSZH sheathing, each installation must be considered on its own merits. In order to offer low smoke, zero halogen properties, the jacket of an LSZH cable uses a high percentage of flame retardant additives (fillers). This can impact properties such as flexibility, chemical and water resistance &#; so bear this in mind when weighing up the needs of your project.
For a cable to be verified as LSZH, it must undergo a series of performance and compliance tests to ensure it meets European and international standards. Here are some of the key standards and testing procedures that cable buyers should seek to confirm their cables are in compliance with.
IEC/EN -1/2 specifies a smoke density test performed inside a 3-cubic metre chamber. While burning PVC has been found in testing to reduce light visibility to 10% (i.e, the thickness of the smoke obscures overall vision by 90%), certified low-smoke cables will have a minimum light transmittance of 60%. In the event of a fire in an enclosed space, this ensures that escape routes remain unobstructed and in reasonably clear view.
IEC/EN -1 stipulates that emissions of the highly toxic, acid gas hydrogen chloride (HCI) by LSZH cables must not exceed 0.5%. When PVC is burned, as much as 30% of emissions released can be HCl. To certify a cable as LSZH, a testing process sees 1g+/-0.005g of cable insulation material placed in a tube furnace and heated to 935ºC for 30 minutes. The gases produced are absorbed into a catch solution, which is then made up into a litre of liquid.
Following a similar process, IEC -2 measures the pH of the solution and tests its conductivity values. Low Smoke Zero Halogen materials are defined as having a pH no less than 4.3 and a conductivity not exceeding 10µS/mm.
N2XH cables in both Class 2 and Enhanced Flex Class 5 variants are low voltage 0.6/1kV low-smoke, zero halogen power cables with a flame-retardant, non-corrosive FRNC outer sheath to reduce fire propagation risk and protect sensitive equipment. These cables are available with CPR classifications suitable even for installations designated high-risk. Manufactured to IEC -1. Eland Cables holds the largest stockholding of N2XH cables in Europe, making them available on-demand for projects.
N2XSH & NA2XSH European Medium Voltage LSZH power cables in 6/10kV, 12/20kV and 18/30kV have either copper or aluminium conductors and are also available with additional waterblocking layers. Manufactured to IEC -2 and available direct from stock.
BS & BS AWA single core and SWA multicore LSZH armoured cables (0.6/1kV and 6.35/11kV / 19/33kV respectively) providing additional mechanical protection for buried installations, to British standards. Available from stock for next-day delivery
EN -7 RE-2X(st)H LSZH instrumentation cables to the European standard, available with collective screening or with PimF (pairs in metal foil) individual screening. Available from stock across a large range of sizes.
As a market-leading supplier with a comprehensive range of cables for power, data & control applications, Eland Cables are well-positioned to understand the importance of selecting the correct LSZH cable for your project.
We're committed to assuring product quality and compliance for each and every one of our LSZH cables. Rigorous testing is undertaken in The Cable Lab, our globally recognised facility holding IEC/ISO and IECEE CBTL, including IEC -1 and IEC -2 for halogen gas emissions testing and gas acidity testing, as well as vertical flame testing to IEC -1-2 to assure self-extinguishing properties meet the parameters of the standard.
To discuss your specific requirements, get in touch with one of our experts today.
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When talking about communication cables, we commonly use terms like LSZH and PVC to describe them. These two terms describe the chemical compounds used in production of the cables. Do you exactly know what they really mean? Or more importantly, which one is better for your project? In this article, we are going to explain these frequently asked questions, by analyzing and comparing LSZH and PVC cables.
LSZH &#; Short for low smoke zero halogen, LSZH is a kind of cable built with a jacket material free from halogenic materials (such as chlorine and fluorine), since the toxic nature of these chemicals when burned. The term &#;low-smoke, zero-halogen&#; describes two distinct properties of a cable compound. The term &#;low- smoke&#; describes the amount of smoke which a compound emits when burned, while &#;zero-halogen&#; describes the amount of halogens used to make the compound. Terms like LSOH, LSHF and LSNH are all proper references for cables possessing low-smoke and zero-halogen properties.
PVC &#; Polyvinyl chloride (vinyl), a general-purpose plastic jacket material used for cables. Features low in cost and flexible, PVC cable is widely used in applications such as computers, communications and low voltage wiring. In the world of cabling, &#;PVC&#; is often used to denote a cable that is not suitable for use in a plenum airspace. PVC can potentially be dangerous in a fire situation, releasing heavy smoke and hydrogen chloride gas, which poses a great threat to human health electronic devices. PVC cables often have a CM, CMG, or CMR rating as defined by the National Electrical Code (NEC).
Differences between LSZH and PVC Cable
Judging from the physical appearance, the difference between LSZH and PVC cable is very distinct. A PVC cable feels soft and it is smooth, whereas an LSZH cable feels rough since they contain the flame retardant compound and it is stiffer. LSZH cables are more aesthetically appealing than PVC cables. In addition to this, LSZH cable differs from PVC one in at least three aspects:
Cost: LSZH cables are slightly higher in cost than some PVC cables, but they are much safer when it comes to human health and sensitive and expensive electronic equipment. And this should be considered when comparing the cost.
Flexibility: Comparing with PVC compounds, there is a limited range of compound flexibility available for LSZH compounds, so LSZH cable is not recommended for robotic or continuous flex applications.
Heat: When a PVC cable is set on fire, it emits chemical fumes, acids and other toxic gases, which are both corrosive and harmful to human beings and environments. As for LSZH cable that has a flame-resistant jacket, it doesn&#;t emit these chemical substances even if it burns or exposed to high sources of heat. And it can reduce the amount and density of the smoke.
When Do I Use LSZH or PVC?
It is feasible that LSZH and PVC have equally effective performance in modern buildings. So the decision on which one to choose actually depends on the situation, that is to say, where you are going to run the cable.
PVC cable has been used in built environment for power and control applications for decades. It is commonly used for horizontal runs from the wiring center, or for vertical runs between the floors&#;but only if the building features a contained ventilation system running through the duct work.
LSZH cable would be more appropriate for places where fire presents a hazard to occupants. We know that the primary danger in the event of a fire is not the fire itself but the smoke and gas produced. Therefore, it is vital that the materials and products that are installed contribute as little smoke and gas as possible when burnt. LSZH cable can be employed in the following situations:
Confined spaces with large amounts of cables in close proximity to humans or sensitive electronic equipment, such as submarines and ships.
Mass transit, central office facilities and telecommunication applications.
Conclusion&#;
Even though PVC cable still reigns supreme in wire and cable industry, the use of this has decreased over the past years. On the other hand, LSZH cable technology has advanced significantly, it is well suited to some applications mentioned in this article. Your cabling choice always relays on your specific condition, while to consult with wire and cable experts can also be beneficial.