LSZH Cable &#; The Ultimate FAQ Guide

Low Smoke Zero Halogen or LSZH is a common term you&#;ll come across when buying or working with cables.

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It&#;s not merely a definition of materials or characteristic of cable, but a highly important distinction, which could ultimately mean the difference between life and death.

LSZH cables are also sometimes referred to as ZHLH or simply halogen-free cables.

This definition of the cable basically helps determine the materials that go into the insulation and sheathing of the cable.

Any materials that are not classified as LSZH do not make the cut.

Countries and industries across the world have strict standards for cable materials, and LSZH is becoming increasingly popular because of the safety these cables offer.

What is LSZH Cable?

Low Smoke Zero Halogen or LSZH cables are those that don&#;t contain any halogens in their material composition and don&#;t produce smoke in case of fire.

These cables produce a very limited amount of smoke and toxic gases, especially acid gases.

These cables are good for use indoors and in hazardous environments where the threat of fire and harmful gases may be high.

They are essentially fire-retardant cables, too, as they self-extinguish.

However, they are not completely fire-resistant, which means they can burn and bear damage if the fire from the source is continuous.

Low smoke and zero halogen are two separate elements.

So it&#;s important to understand them individually.

Low Smoke

Low smoke pertains to the cable jacket producing limited smoke.

It doesn&#;t mean that it won&#;t burn or not produce any smoke at all.

It only means that the smoke wouldn&#;t be of dangerously high levels to become toxic, reduce visibility, and hamper rescue efforts.

This is entirely dependent on the jacketing material in the cable, as the sheath is the first layer to come in contact with fire.

In most cases, the flame isn&#;t as dangerous as the smoke and gas it produces.

In indoor settings, most casualties in fire may be caused because of the smoke because it creates respiratory difficulties, reduces the visibility of exit routes, and creates panic.

For instance, tests show that PVC (polyvinyl chloride) can reduce visibility by as much as 50 percent when burning. In half an hour, it can become as high as 90 percent.

This makes PVC high-smoke material; however, there are low-smoke versions of it with appropriate additives.

Many international standardization and certification bodies have specific tests and benchmarks to gauge the smoke emission of materials.

Cables must pass those tests to qualify as low smoke cables.

Zero Halogen

Zero halogen simply means that no component, primarily insulation and sheathing, should have any halogens in their composition.

Halogens consist of five elements, including Chlorine (Cl), Bromine (Br), Iodine (I), Florine (F), and Astatine (At).

The reason why halogens are emitted from cables is that when the cable is on fire, these can produce toxic gases or liquids, such as highly acidic HCl.

The best example of a material that&#;s not zero halogens is PVC, as it contains Chlorine.

Tests show that PVC can produce as much as 30 percent HCl in case of a fire.

What is the Difference Between LSZH Cable and LSF Cable?

Some cables are labeled as LSF (low smoke and fume), which is different from LSZH.

It only covers part of the equation, as LSF cables might still have halogens in their materials.

For instance, PVC cables that are low smoke are LSF but not LSZH.

Those cables still pose the threat of halogen gases when burning.

Usually, LSF cables have additives to help make them low smoke and low halogen, but they are not zero halogens.

LSZH cables usually follow even stricter standards than LSF cables.

LSF cables can emit halogen acids far beyond the limits set for LSZH cables.

LSZH Materials

There are two kinds of LSZH materials essentially: thermoplastic LSZH and thermoset LSZH.

Thermoplastic LSZH materials can be molded by heating many times, whereas thermoset LSZH materials can only be molded once.

Hence, they are not recyclable.

While PVC is the most common thermoplastic, it&#;s not an LSZH, as it contains Chlorine.

On the other hand, ethylene-propylene rubber (EPR) and crosslinked propylene (XLPE) are LSZH.

These two materials are very common in cables along with PVC.

It&#;s worth noting that LSZH thermoset materials may not have as high resistance to flames as chlorinated thermosets.

This is one tradeoff when using LSZH cables, as their thermal range may be slightly lower than those with halogens.

That said, crosslinked materials such as XLPE have a much higher thermal range.

The LSZH material you choose comes down to other factors as well, such as voltage rating of the conductor, environmental conditions, and application-specific requirements.

However, the material must meet the set requirements and tests.

What are the Applications of LSZH Cable?

LSZH cables are used both indoors and outdoors, but mostly indoors where it&#;s usually hard for the smoke to escape.

Just by that requirement, the applications of such cables are many.

Here are some examples:

1. Public areas
2. Houses
3. Industrial plants
4. Tunnels and underground rail networks
5. Transport (cars, trucks, buses, aircraft, trains, and ships)

LSZH cables may be used in any place where the laws and regulations require cables to use LSZH materials.

Many countries and city governments, as well as safety boards, mandate that contractors and construction companies use such cables for all indoor wiring.

This is why LSZH is becoming a standard for indoor cable applications.

What are the Advantages of LSZH Cable?

There are obvious advantages to using LSZH cables:

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• Less Smoke: The fact that LSZH produces very limited smoke makes it ideal for indoor areas and those with poor ventilation. If a fire breaks out in a home and the cables catch on fire, if they are low smoke, they won&#;t add to the smoke already being produced by other structures and items in the home.
• Self-extinguishing: LSZH cables are mostly fire-retardant, which means they don&#;t propagate fire. While they may not resist it completely, they do their best to avoid getting burned if the fire is not sustained.
• No Harmful Gases: Even if the cables have caught fire and are burning, they won&#;t produce any harmful gases that may poison the people on the premises. This makes these cables so much better than cables that have halogens, such as PVC cables.
• No Delay in Rescue: Smoke can hamper rescue efforts in case of a fire by reducing the visibility acutely. It may make it hard for people trapped to get to exit routes and for fire rescue teams to get inside the premises. With low smoke, the visibility may be just enough for the rescue teams to conduct their safety operations and save lives.

What are the Standards of LSZH Cable?

There isn&#;t any universal definition or standard when it comes to LSZH cables.

However, most international standardization bodies have tests and standards for cable manufacturers to comply with in order to certify their cables as LSZH.

Manufacturers must test the cables according to the test describes by those standards.

For instance, the standard BS prescribes a test for smoke density.

The test is performed in a 3 x 3 x 3 cubic meter chamber.

A white light is passed through the chamber at a particular height so as to measure how the smoke hinders the transmittance of light.

The test requires the minimum transmittance to be 60 percent.

Similarly, another British cable standard BS EN requires HCl emissions from the cable to be under 0.5 percent for it to quality as zero-halogen.

International Electrotechnical Commission (IEC) has its own set of standards and tests for qualifying cables as LSZH.

Here are the three most frequently used standards in the cabling industry:

• IEC -1 (Flammability)
• IEC -2 (Smoke emission)
• IEC -1 and IEC -2 (Acid gas emissions)

The IEC -1 test for flammability is similar to that of BS , which involves a 3 cubic meter chamber and light transmittance.

The IEC -1 test involves burning the cable for 60 minutes and collecting any halogen acid produced.

It should not exceed 5 mg/g.

The second part, IEC -2, measures conductivity and pH.

The pH value should not be less than 4.3 and the conductivity value should not exceed 10 uS/mm.

LSZH cables also comply with the European Union (EU) Restriction of Hazardous Substances (RoHS) directive.

Other standardization bodies around the world may have similar tests for cables to qualify as LSZH.

The cables are not officially LSZH unless they meet the standards set by one of these bodies.

Conclusion

LSZH cable plays a vital role in ensuring the safety of infrastructure and human life.

While they are not immune to fire, they can reduce the danger.

Low smoke and no risk of acidic gases and fluids make these cables a safer option for indoor cabling.

There are strict standards for such cables, especially on marine shipboard, that must be fulfilled for the cable to be labeled LSZH.

The cable manufacturers must comply with those specific standards for the market they are serving.

As for the cable type and materials, that depends on the application they are for.

Cable Jacket: Should I Choose LSZH or PVC?

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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. As we might be rather familiar with these widely used terms, 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.

What LSZH and PVC Stand for?

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 known 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 which 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.

Source: http://www.china-cable-suppliers.com/cable-jacket-choose-lszh-pvc.html

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