The "Low Smoke" Element of LSZH Cables
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.”
Tests indicate that burning PVC can reduce visibility by up to 50% within 10 minutes. After 30 minutes, visibility can decrease by as much as 90%, making escape unnecessarily difficult.
In comparison, BS EN specifies a smoke density test conducted inside a chamber measuring 3m x 3m x 3m, known as the 3 metre cube test. This test measures the reduction of light transmittance from one side of the chamber to the other. For a cable to be categorized as low smoke, it must typically have a minimum light transmittance of 60%.
If you are looking for more details, kindly visit SUNUA.
The "Zero Halogen" Element of LSZH Cables
Burning PVC and other cable compounds emit harmful chemicals, including hydrogen chloride (HCl), which is extremely toxic. When mixed with water, HCl forms hydrochloric acid, a toxic and corrosive substance. In the case of PVC, up to 30% of emissions can be HCl.
BS EN dictates that emissions of HCl by LSZH cables must not exceed 0.5%.
LSZH vs. LSF Cables
There is a common misconception that low smoke and fume (LSF) cables are the same as LSZH cables; however, this is not true. Confusing the two can be life-threatening in the event of a fire.
Unlike LSZH cables, LSF cables are made from PVC compounds. When labeled as low smoke and fume cables, it is due to the manufacturer modifying the compound with additives to reduce (but not eliminate) smoke and HCl emissions. In contrast, LSZH cables must adhere to strict standards, while LSF cables have no such regulations. Consequently, LSF cables can emit HCl levels exceeding 20% when ignited.
As a leading rail and metro cable supplier, Eland Cables understands the implications of selecting LSZH cables for various industries. Please contact our technical team to discuss your specific needs and our extensive range of LSZH cables tailored for applications in building and construction, oil and gas, marine, and offshore sectors.
What is LSZH?
Many industries are experiencing a growing demand for Low Smoke Zero Halogen (LSZH) cables. The primary driver for this increase is the concern for safety regarding both people and electronic circuits during fires. Environmental protection and enhanced requirements from local and international communities have also escalated the demand for LSZH cables.
This heightened awareness of the negative effects from halogens when exposed to flames has led to the development of this cable type.
We answer some frequently asked questions surrounding LSZH cables.
What is LSZH?
LSZH stands for Low Smoke Zero Halogen. It refers to a category of jacket and insulation compounds that do not contain halogens in their chemical composition. The terms LSOH, HFFR (Halogen Free Fire Retardant), and NHFR (Non Halogenated Fire Retardant) are often used interchangeably.
Are you interested in learning more about lszh compounds? Contact us today for expert consultation!
What are Halogens?
Halogens comprise a group of elements characterized by being one electron short of a stable molecule. Consequently, they are highly reactive and will combine with other elements to gain the missing electron.
Halogens react with metals to form salts; for example, table salt is a mixture of the halogen chlorine and the metal sodium. Additionally, when mixed with water, free hydrogen binds with halogens to create acids. One of the most common acids is hydrochloric acid, derived from hydrogen and chlorine.
Why are Halogens Used for Flame Retardancy?
In some polymers, the inclusion of a halogen atom can provide flame retardant properties. Polyvinyl chloride (PVC) is a common example that contains chlorine. When burned, chlorine is released and displaces oxygen from the flame, effectively smothering the fire.
Some flame retardant polyethylenes have bromine, another halogen, incorporated to enhance flame retardancy.
What are the Side Effects of Halogens When Exposed to Flames?
When combined with hydrogen, halogens create acids that are toxic to animals and plants. Chlorine, for instance, is used in controlled ways to sterilize water by eliminating microbes and bacteria. Previously, iodine-based solutions were also utilized for this purpose.
What About PVC?
When PVC burns, it releases chlorine that can chemically react with hydrogen to form an acid. This acid can cause severe harm to the lungs and eyes of those attempting to escape the fire, and can also damage equipment that may appear undamaged after the fire. Historical data indicates that equipment located several rooms or floors away from a small fire may fail months later due to attacks by halogen acids or salts.
What are the Benefits of Using LSZH Cables?
LSZH compounds do not contain halogens; instead, they release water or other non-toxic substances to extinguish flames. As a result, LSZH cables are safer for both individuals and the environment.
Where are LSZH Cables Predominantly Used?
LSZH cables can be utilized wherever normal cables are employed. They are particularly advantageous in indoor or restricted environments, where their low toxicity in the event of a fire is critical. This makes them ideal for use in tunnels, offices, exchanges, and data centers.
Can I Still Achieve My Green Star Credits with LSZH?
Yes, LSZH cables are suitable for Green Star applications.
LSZH cabling is the safest option for plenum use and other scenarios where smoke accumulation may endanger individuals, as no harmful toxins are released. In line with our commitment to sustainability and reducing environmental impact, Garland is proud to offer Low Smoke Zero Halogen cables as part of our environmentally-friendly, Green Star-rated range.
Comments
0