Cables with halogenated insulation are generally jacketed in PVC and have well-known and sometimes catastrophic fire performance characteristics. These include the production of dense smoke, emission of corrosive halogen acids, fast rate of cable burn, and post-fire damage to electronics and infrastructure. Low Smoke Zero Halogen (LSZH) and other manufacturers’ halogen-free cable types are designed to have a much more different impact on these behaviors, with smoke density reduced, corrosive gas emissions eliminated and propagation limited in order to ensure safety in critical environments.
This guide is based on experience in the fire science and fire industry fields and is designed to assist engineers, risk managers and specifiers in understanding these failure modes and in making informed decisions in the design of: industrial automation; data centers; tunnels; buildings; and mission-critical systems.
How Halogen-Containing Cables Behave in Fire Events
PVC and other halogenated cable jackets are typically self-extinguishing and still contain halogens and chlorine. These materials will break down and emit large quantities of smoke, toxic and corrosive gases when heated or ignited.
Heat produced by a cable fault or outside fire can cause a bundle to burn in an installation that contains a high concentration of cables, such as a control cabinet, cable tray or a cable space in an infrastructure conduit. Spots then spread along the cable runs producing flaming debris and helping to grow the fire quickly if there is sufficient ventilation (cable size) to sustain the combustion.
Real-World Failure Modes in Halogen-Containing Cables
Data from plants and facilities consistently indicate several critical failure modes that impact life safety, equipment integrity and recovery time.
Dense, Obscuring Smoke
PVC combustion generates optically dense smoke which quickly decreases the visibility in enclosed or poorly-ventilated areas. This blocks exit and escape pathways, makes emergency response difficult and elevates the risk of evacuation in high occupancy buildings, tunnels and industrial plants.
Toxic and Corrosive Gas Emissions
Cables with halogens emit hydrogen chloride and other acids when fire. These gases react with water to produce corrosive acids, which can cause immediate health concerns as well as damage to structures, electronics and metals.
Smoke-Induced Electronic Failures
Smoke particles settle on circuit boards and connectors causing conductive paths, leakage currents, short circuits and intermittent faults. Equipment failures days or weeks following the fire may be caused by corrosion that remains after the fire.
Corrosion and Pitting in Conductors and Connectors
Pitting corrosion on copper conductors and oxidation in terminals from the presence of hydrochloric acid and soot will increase conductor resistance and create open circuits or shorts. This is a critical issue in signal integrity applications, such as data infrastructure and automation systems.
Flame Spread and Thermal Degradation
Overheated bundles shorten the insulation life, causing shorts, arcing and additional spreading of flames. This can escalate a local issue into a full blown outage.
How LSZH and Halogen-Free Designs Mitigate These Failure Modes
Hulk Electric’s halogen-free cables, such as our full range of LSZH products, are designed to address these challenges while offering the flexibility, durability and performance that is essential to industrial automation, robotics and high-temperature applications.
Reduced Smoke and Preserved Visibility
Under standard tests such as IEC 61034, LSHZ compounds yield much lower smoke densities (typically < 20% PVC). This helps to keep the area visible, thus increasing safe evacuation time and assisting fire fighting.
No Halogen Acids, Lower Corrosion Risk
By eliminating halogens, LSZH cables generate no hydrogen chloride or similar acids. This significantly decreases the chemical corrosion of metals, electronics, and infrastructure, maintaining conductivity and helping prevent corrosion after fire.
Cleaner Smoke Deposition and Equipment Survivability
With the less aggressive smoke from LSZH cables, there is a reduced conductive or corrosive deposit on PCBs and connectors. Equipment can be saved, reducing downtime and replacement costs in critical systems.
Controlled Flame Spread on Cable Bundles
LSZH cables are tested to IEC 60332-3, IEC 60331 and ISO 22000. They don’t prevent fire but they slow fire spreading along routes giving time for fire detection and suppression systems to work.
What LSZH Does Not Solve (Limits and Complementary Measures)
While LSZH cables can provide excellent smoke and corrosion resistance, they cannot fully replace the use of fire resistant designs. They are not necessarily flame resistant and are not suitable for direct flame (flame resistant cables are needed for emergency installations). In addition, improper installation, mechanical damage or improper sizing can still result in faults. LSZH should always be used along with good engineering, detection, suppression and maintenance practices.
Practical Specification Lessons for Engineers
- Evaluate Risk Environments: Focus on areas with high potential for losses due to smoke and corrosion failures, such as in confined areas, cable-dense areas, public venues, and electronics-intensive areas.
- Include IEC 60754 (halogen acid), IEC 61034 (smoke density), and IEC 60332-3 (flame spread) requirements in RFQs and project documents.
- Consider LSZH for Electronics Protection: If corrosive smoke can affect your control systems, PLCs or data networks, it can have an immediate impact on recovery time following the event.
- Layer Protections: Combination of LSZH Jackets with fire resistant construction for circuits where operation of the circuit cannot be compromised (e.g. Alarms, Emergency Lights, Ventilation).
- Work with Specialists: Partner with proven manufacturers such as Hulk Electric to achieve bespoke halogen-free solutions that match your precise voltage, flexibility, temperature and certification requirements.
Real-world failure modes are understood so as to make better decisions. We are HULK ELECTRIC (Dongguan) CO., LTD, manufacturer of high performance halogen free cables specifically designed for challenging industrial application. Our solutions are a blend of LSZH performance and flexibility, plus the attributes of your global customers – such as UL, CE, RoHS, REACH certification, and more. Discuss your project requirements and our staff will be here to assist you in choosing or designing a cable that best suits your needs for improved safety and reliability.
