Why use LSZH?

Many industries have seen an increasing demand for Low Smoke Zero Halogen (LSZH) cables. Main driver of this increase is the concerns for the safety of people and electronic circuits during fire. Environmental protection and an increase in requirements / specifications from local and international communities has also heightened the demand for LSZH cables.

This increased awareness of negative side effects arising from halogen when exposed to flames has lead to this jacket type being designed.

We answer some of the more frequently asked questions surrounding this cable type.

What is LSZH?

LSZH stands for Low Smoke Zero Halogen. It refers to a group of jacket and insulation compounds that do not contain halogens within their chemical makeup.  The terms LSOH, HFFR (Halogen Free Fire Retardant) and NHFR (Non Halogenated Fire Retardant) are often used interchangeably.

What are Halogens?

Halogens are a group of elements that are characterized by being 1 electron short of forming a stable molecule, as a result they are highly reactive and will combine with other elements in order to gain this missing electron. Halogens react with metals to form salts, common table salt is a mixture of the halogen chlorine and the metal sodium. When mixed with water, free hydrogen in water will combine with halogens to make acids. One of the most common acids being Hydrochloric acid which is a mixture of hydrogen and chlorine. Halogens can also mix with hydrogen (present in water) to create an acid. Hydrochloric acid used to acid etch concrete is a mixture of hydrogen and chlorine.

Why are Halogens used for flame retardancy?

Within some polymers, the introduction of a Halogen atom can produce a flame retardant capability. Poly-Vinyl-Chloride (PVC) is a common example and contains chlorine. When burned the chlorine is released and displaces oxygen from the flame thus helping to smother out the fire. Some flame retardant polyethylenes have bromine, another halogen, added in order to assist with flame retardancy.

What are the Side effects of Halogen when exposed to flames?

When combined with Hydrogen, Halogens form acids. These acids are toxic to animals and plants. Chlorine is an example where this characteristic is used in a controlled way to sterilize water by killing off microbes and bacteria. In the past, solutions based on the halogen iodine were also used for this application.

What about PVC?

When PVC burns, it releases Chlorine which is now free to combine with hydrogen to form an acid. This acid can burn lungs and eyes of people trying to flee the fire. It can also attack equipment that was not destroyed in the fire. Historical experience has shown that equipment located several rooms or floors away from a small fire can fail many months later due to attack by either halogen acids or salts.

What are the benefits of having LSZH cable?

LSZH compounds contain no halogens and instead rely on releasing water or other non-toxic compounds in order to put out a flame. As a result, they are safer for both people and the environment.

Where are LSZH cables predominantly used?

LSZH cables can be used anywhere a normal cable can be used. Typically they are of greater benefit in indoor or restricted spaces where their low toxicity in a fire is a great benefit. This means that they often find use in tunnels, offices, exchanges and datacentres.

Can I still achieve my Green Star credits with LSZH?

Yes, LSZH cables are suitable for Green Star applications. LSZH cabling is the safest choice for plenum use and any other applications in which smoke is likely to both build up and come into contact with people, since no harmful toxins are actually released. In line with our commitment to sustainability and reducing their impact on the earth, Madison Express offers Low Smoke Zero Halogen cables by Garland as an extension to their environmentally friendly Green Star rated range.