LSZH Cable – Low Smoke Zero Halogen Cable

Low Smoke Zero Halogen LSZH Cable

What is LSZH cable?

LSZH cable stands for Low Smoke Zero Halogen cable, sometimes also abbreviated as LSOH. They are intended for use in applications where smoke emissions and toxic fumes could pose risks to human health and/or vital equipment in a fire situation. These cables are also sometimes referred to as LSHF (Low Smoke Halogen Free) cables.

LSZH cables produce extremely low levels of smoke and toxic fumes with zero acidic gases. This is unlike PVC cables and those manufactured with other insulation materials, which can produce large amounts of thick black smoke, toxic fumes and acidic gas when subjected to fire.

LSZH cables are often specified for the wiring of equipment fitted indoors, particularly in public areas, and in poorly ventilated and risk environments. This can include hospitals, schools, shopping centres, cinemas, police and fire stations and underground railway networks.

Low Smoke Emissions

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.”

In tests carried out, burning PVC has been found to reduce visibility in the immediate area by as much as 50% within 10 minutes. After 30 minutes, visibility can be reduced to as little as 10%, making evacuation of the area both difficult and dangerous.

In contrast, LSZH cables under the BS EN 61034 specified 3 metre cube smoke density test, have an approximately 60% minimum light transference.

Zero Halogen

The burning of PVC and other insulation compounds produces several chemicals, including hydrogen chloride (HCl), a highly toxic compound. Additionally, when combined with water, HCl forms hydrochloric acid; a substance which is both toxic and corrosive. With PVC, as much as 30% of the emissions can consist of HCl.

In the case of LSZH cables, BS EN 60754 stipulates that emissions of HCl must not exceed 0.5%.

LSZH vs LSF Cables

There is a common misconception that low smoke and fume (LSF) cables and LSZH cables are one and the same. This is completely incorrect and any confusion between the two could be life-threatening in the case of a fire.

LSF cables are manufactured using PVC compounds. When cables are labelled as “Low Smoke and Fume” or “LSF”, it means that the manufacturer has modified the compound with a number of additives in order to reduce smoke and HCl emissions. This however does not eliminate them.

While Low Smoke Zero Halogen Cables are subject to strict standards, LSF cables have no standards covering them. In consequence, LSF cables have been found to emit HCl levels in excess of 20% when subjected to fire.