LSZH cables (Low Smoke Zero Halogen) are essential in any application where human safety and equipment preservation during a fire are paramount—data centers, transit systems, tunnels, hospitals, and public buildings. Understanding LSZH cable properties helps you specify the right cable for safety-critical applications.

What Is LSZH Cable?

LSZH cable refers to cable with jackets and insulation made from materials that, when burned, produce minimal smoke density and zero halogen gases (hydrogen chloride, hydrogen fluoride, etc.). The primary alternative materials are:

• Polyolefin compounds — Cross-linked or non-cross-linked polyethylene/polypropylene-based
• EPR (Ethylene Propylene Rubber) — Common in industrial power cables
• PEEK (Polyether Ether Ketone) — High-performance for extreme environments

The zero halogen property is measured by the acid gas liberation test (IEC 60754 series) — LSZH cables must produce less than 0.5% halogens by weight when burned.

Why LSZH Matters in Fire Scenarios

Smoke Density

In enclosed spaces—tunnels, data centers, subway stations, ships, aircraft—dense smoke from burning PVC cables is the primary cause of fire fatalities. Smoke obscures evacuation routes and emergency lighting. LSZH cables tested to IEC 61034 produce dramatically less smoke, improving evacuation survival rates.

Zero Halogen Toxicity

When PVC burns, it releases hydrogen chloride (HCl) gas—which dissolves in moisture to form hydrochloric acid. This acid damages lung tissue (even at low concentrations) and corrodes sensitive electronics. In a data center, burning PVC cables can destroy millions in server equipment through acid corrosion—not just from heat.

Fire Gas Danger

Beyond acid gases, standard PVC cables release polycyclic aromatic hydrocarbons (PAHs) and dioxins at high temperatures. LSZH materials minimize these toxic byproducts. EN 50267 / IEC 60754 tests measure acid gas content, conductivity, and pH value to verify zero-halogen compliance.

LSZH Cable Standards and Ratings

IEC 61034 — Smoke Density

Measures light transmittance through smoke from burning cable samples. Pass criteria: minimum 60% light transmittance (IEC 61034-2). High-performance LSZH cables achieve 80-90% transmittance.

IEC 60754-1 — Acid Gas Emissions

Measures halogen content by weight. Pass criteria: less than 0.5% halogen by weight for zero-halogen designation.

IEC 60332-3 — Flame Spread on Bunched Cables

Tests flame propagation on multiple cables installed in bunched configurations (worst-case real-world scenario). Different categories (A, B, C, D) based on cable volume per meter. Tunnel and transit applications typically require Category A (highest fire load).

LSZH vs Other Cable Jacket Materials

Applications Requiring LSZH Cables

• Data centers and server rooms — Protect equipment from acid corrosion in fire scenarios
• Transit systems — Tunnels, metro stations, airports (EN 45545 standard)
• Ships and maritime — IEC 60092 marine standards require low smoke, halogen-free
• Hospitals — Life safety circuits, evacuation system wiring
• Enclosed industrial — Mining, tunnels, offshore platforms

Frequently Asked Questions

Is LSZH cable always better than PVC cable?

For fire safety in enclosed spaces, yes—LSZH is clearly superior. However, LSZH cables are more expensive, slightly less flexible, and may have reduced mechanical strength compared to PVC. In outdoor applications without fire safety concerns, PVC or PUR cables may be more cost-effective.

Does LSZH mean completely smoke-free?

No. LSZH means reduced smoke density and zero halogen gases, not no smoke. All organic materials produce some smoke when burned. LSZH cables produce significantly less smoke than PVC cables, but they still generate some combustion products.

Can LSZH cable be used in flexible or robot applications?

LSZH compounds are generally less flexible than PVC or PUR. For continuous flex applications (energy chains, robot arms), LSZH cables may have shorter flex life than PUR cables. In fire-safety-critical flex applications, specify LSZH with high-flex construction (Class 6 conductors) and verify flex cycle testing data.