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What are Low Smoke Zero Halogen (LSZH) Cables?

There is a growing trend in the use of Low Smoke Zero Halogen (LSZH) cables with casing materials that are safer in the event of fire.

As the name suggests, LSZH cables produce less dense smoke and virtually no highly toxic gases called halogens, unlike traditional materials such as polyvinyl chloride (PVC) and fluorinated ethylene propylene rubber (FEP).

That being the case, it seems very reasonable that designers should always choose to use these types of cables, but the real decision is far more complicated, and it is imperative that electrical engineers understand LSZH cables, where they are suitable, and how to select and apply them, which is crucial.


LSZH cables are not suitable for all applications

Keep in mind that while we have found cables using halogenated compounds such as PVC and FEP to be hazardous in the event of fire, LSZH cables are not a universal solution to replace them for the following reasons. 

First, PVC and FEP-based cables also have important advantages that cannot be ignored, and in open spaces where fumes and gases can spread rapidly, there are not many advantages to using LSZH cables to replace them. 

In addition, cables are often not the only source of plastic in the event of a fire, and PVC and FEP-based cables are fire-resistant, so they are relatively less responsible for fires among many factors.


PVC and FEP based cables are less expensive than LSZH cables and offer excellent electrical performance for a wide range of applications with excellent electrical properties in both dry and wet environments. 

They are also highly flexible, have a long service life, can withstand extreme temperatures and chemicals, and are extremely durable. In short, LSZH cables are best suited for scenarios where traditional cables can be hazardous. They are not intended to replace traditional cables in all applications.

The combustion and flame properties of PVC and FEP in cable Sheath, dielectric materials, and other components have been known since the 1970s, and by around 1980, cables with alternative materials had been used in military and nuclear systems. But in 1987, a fire at London's King's Cross Underground station killed more than 30 people and injured more than 100, drawing global attention.


An investigation into the fire at London's King's Cross Underground station has revealed that the burning of a large number of cables has produced thick black smoke and toxic gases, making it difficult for people to escape.

Subsequent investigations showed that a match that fell on the elevator was the cause of the fire. Many reasons led to the spread of the fire which claimed many lives. 

One of the reasons is the burning of a large number of cables, producing dense black smoke and toxic gases, making it difficult for people to escape. This fire is believed to have prompted the industry to develop cables that perform better and are safer in fires.

As a result of this accident, the use of PVC cables was banned on the London Underground, and within a short time, LSZH cables were widely used by other EU members. The U.S. has taken longer to promote the use of such cables for a number of reasons, including cost considerations, conflicting standards, debates about where to apply, and more. Later, these issues were gradually resolved, and PVC and FEP-based materials were being replaced in the applications that benefited the most.