Low smoke zero halogen or low halogen free smoke (LSZH or LSOH or LS0H or LSFH or OHLS) is a material classification typically used for cable sheaths in the wire and cable industry. The LSZH cable sheath consists of halogen-free thermoplastic or thermoset compounds that emit limited smoke when exposed to high heat sources.
The first commercial thermoplastic LSZH material for cable sheathing was invented in 1979 by Richard Skipper and patented by Raychem Corporation. The present invention does not allow the formation of a coal which allows sufficient inorganic filler to suppress fire, aluminum trihydrate (ALTH) into a suitable thermoplastic matrix and a coal that reduces the release of toxic carbon gases and also smoke and carbon particles solved the difficulty. electrical insulation properties and physical properties required by the final application. The preferred inorganic filler to provide flame retardation continues to be aluminum trihydrate (ALTH). In the event of fire, this material reacts endothermically.
Al (OH) 3 → Al2O3 + 3H2O (180 [deg.] C.)
This absorbs heat energy and leaves steam when the compound reaches a certain temperature. It is critical that the decomposition of the polymers used to transport the filler takes place at approximately the same temperature. The steam prevents the burning of the developing gases and helps to form a layer of coal that protects the remaining material and traps the particles. The required high filler level (ıcı60%) also changes the base polymer, which reduces the total amount of fuel available for combustion.
The low-smoke zero-halogen cable significantly reduces the amount of toxic and corrosive gas emitted during combustion. When illuminated, a low-smoke zero-halogen cable emits a less-emitting, less optically dense smoke. During the fire, a low-smoke cable is required because it reduces the amount and intensity of the smoke, which makes it easier for passengers to leave an area, while increasing the safety of fire extinguishers. This type of material is typically used in poorly ventilated areas, such as aircraft, wagons, tanks, submarine and marine installations, submarines or ships. It is also widely used in the railway industry where high voltage or trace signal wires are required to enter and enter underground tunnel systems. The nuclear industry is another area in which the LSZH cables are used and used in the future. Major cable manufacturers have been manufacturing LSZH cables for nuclear installations since the early 1990s. The construction of new nuclear power plants will definitely involve the comprehensive use of the LSZH cable. This will reduce the likelihood of accumulation of toxic gases accumulating in the areas where personnel work, and the absence of corrosive gases with computer-controlled systems will reduce the chance of fire damage to cables resulting in a short-circuit failure. Since the 1970s, the wire and cable industry has been using low-smoke, low-halogen materials in many applications. The introduction of the thermoplastic LSZH extended its use to accessories such as heat shrink tubing, labeling and fixtures. The aim was to create a wire and cable sheathing system that did not only produce flame retardant but also intense, inhibitory smoke and less toxic or corrosive gases. It was launched after 1982, after heavy black smoke from HMS Sheffield, after being hit by a great missile during the Falklands war. In 1987, the fire in London, which led to the death of 31 people in London underground, King’s Cross fire, such as fire, wire and cable sheath increased awareness of the contribution of fire. As a result, the use of LSZH cables has increased. In recent years, there has been a greater fuel load in the case of fire, with an increase in the amount of cable in residential, commercial and industrial applications, and the LSZH systems have an important role to play in protecting the public. For military applications, the Def Stan 02-711 in the UK and the ASTM E662 in the US are based on ASTM STP (422 pages 166-204), both modified by AMTE, 1967, and in Portsmouth, UK. He took his place in E662. United States. During these tests, a particular material sample is standardized and then exposed to a radiant heat source; The optical density of the given smoke is measured photometrically.
There are several ways of measuring optical density: the highest smoke release rate, the total smoke emitted and the smoke density at various points and times during the test. The results should be below a certain value and the material must be burned to ensure that the material is labeled as low smoke.
These tests are performed under laboratory conditions and do not claim to reproduce the expected range of conditions in a real fire scenario. However, if necessary, it provides a measure of potential fumes emission of materials and the detection of hazardous substances before further testing of the preferred materials.
What’s the difference between PVC and LSZH cables ?
Physically, PVC and LSZH are very different. PVC patchcords are very soft; LSZH patchcords are more rigid because they contain the flame retardant compound, and they are aesthetically more pleasing.
A PVC cable (made of polyvinyl chloride) has a jacket that gives off heavy black smoke, hydrochloric acid, and other toxic gases when it burns. Low Smoke Zero Halogen (LSZH) cable has a flame-resistant jacket that doesn’t emit toxic fumes even if it burns.
LSZH more expensive and less flexible
LSZH cables usually cost more than the equivalent PVC cable, and certain types are less flexible. LSZH cable does have some restrictions. According to CENELEC standards EN50167, 50168, 50169, screened cables must be halogen free. However, no similar regulation yet applies to unscreened cables.
Where do you run the cable?
Whether you choose a riser (PVC), plenum or LSZH jacket depends on where you’re going to run the cable.
PVC cable is commonly used for horizontal runs from the wiring centre. You can use it for vertical runs between the floors – but only if the building features a contained ventilation system running through the duct work.
LSZH cable is used between floors in a building. It has a special flame-retardant coating.
A plenum is a space within the building created by building components, designed for the movement of environmental air.