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Low Smoke Zero Halogen (LSZH) is a material classification of cable jackets. LSZH is also referred to as LS0H, LSOH, LSHF or LSNH. The LSZH materials emits limited smoke and no halogen elements when exposed to extreme temperatures or flames. LSZH is increasingly becoming a standard jacketing material in all the network installations due to this feature.
Previously, PVC or Poly-Vinyl Chloride jacket was used in communication cables, PVC contains chlorine which is a halogen and when exposed to fire, it produces hydrogen chloride. Hydrogen chloride produces hydrochloric acid when combined with water which is often used as fire extinguisher. This acid not only causes physical injury to the personnel stuck inside the fire affected area but also produces corrosive effect on the equipment installed inside the datacenter.
It is to be noted here that the gases produced by burning LSZH materials is also toxic, extra caution must be taken when exposed to burning LSZH materials. The only advantage of using LSZH cables is that the dangerous gas/acid combination is avoided.
There are two types of LSZH cable jackets:
- Thermoset LSZH
- Thermoplastic LSZH
Let us explore the advantages and disadvantages of the above mentioned types.
The Thermoset LSZH cables typically offer improved performance than the thermoplastic LSZH cables. Chlorinated thermoset jackets are commonly used in various applications due to their ability to pass the most rigorous flame tests. LSZH does not have the long track record of performance that chlorinated thermosets possess, and therefore, are questioned about the lifespan and performance of these cables.
Recent advancements in chemistry have allowed manufacturers to develop thermoset LSZH cables that produce the same test results as chlorinated thermosets, such as the IEEE 1202 and UL VW-1 flame tests. A past problem has been the water absorption tests required in many cable standards. LSZH material typically absorbs a greater amount of moisture than non-LSZH material. Moisture absorption affects the physical and electrical properties of the cables. New compounds and processing methods have allowed manufacturers to solve this problem as well.
LSZH cables find their usage in different areas, the most important and practical usage being in the space confined areas, areas with close proximity to human beings and areas where sensitive equipment is installed. Firstly, LSZH cable standards were adopted by military organizations as LSZH cables were a best fit for sub-marines, aircrafts and battle tanks. With the passage of time, LSZH cables are also found in modern datacenters as the modern datacenters contain large amounts of cabling, and are usually enclosed spaces.
LSZH cable technology has advanced significantly. It is very well suited to some of the applications and environments and less suited to some environments due to their specific features. With the on-going research and development work on LSZH cables, it is possible that in the near future, LSZH will become the cabling standard and replace the PVC cabling altogether.
