Low Smoke Zero Halogen (LSZH) Characteristics

LSZH cables show significantly improved performance, when compared with conventional cables, in meeting demands of specific hazards within a fire situation, through the reduction of both harmful acid gas emissions and smoke obs-curation. LSZH cables are particularly suitable for use in buildings and constructions such as hospitals, theaters, shopping precincts, tunnels and public utilities where protection of life, equipment and structures is essential.


Cables rarely initiate a fire situation, but under fire conditions PVC insulated cables can produce copious quantities of vision obscuring smoke and corrosive hazardous acidic gases. In contrast, LSZH cables produce minimal obs-curation smoke and acidic gas and have been demonstrated as complying where applicable with:

Low Smoke Emission

BS EN 50268 IEC 61034

This test measures the smoke emission from electric cables during fire. The test is carried out in a 3m cubed chamber where a cable sample is subjected to fire. The smoke emission and density are measured by transmitting a beam of light across the inside of the chamber to a photo electric cell which measures the amount of light received.


Gases Evolved During Combustion

BS EN 50267, IEC 60754

These international tests were developed to determine the amount of acid gas evolved by burning cable components.

Part 1. This test evaluates the amount of acid gas by % HCl. LSZH cables return values <0.5% HCl, where the best low acid PVC return values of <5.0%.

Part 2. A more sensitive test than part 1. The recommended values of the test state that the weighted pH values should not be less than 4.3, when related to 1 litre of water. The weighted value of conductivity should not exceed 10μs/mm.

Reduced Flame Propagation

BS EN 50266, IEC 60332-3

This test defines the ability of bunched cables to restrict flame propagation when laid in trunking, cable trays or conduit. The test comprises of 3 categories each determined by the amount of combustible material in a 1 metre sample, as shown in the table below.

No. of liters of combustible material in a 1 m sample73.51.5
Exposure to fire in minutes404020

The cable samples are placed vertically next to one another on a vertical ladder tray where they are exposed to fire from a ribbon gas burner for the pre-arranged times. After burning, the samples are wiped clean to examine for char (the crumbling) of the cable surface. The charring should not have reached a height exceeding 2.5m above the bottom edge of the burner.

2018-09-24T13:37:38+00:00 September 24th, 2018|Cable Knowledge, Cable Raw Material|