For industrial automation, robotics and building services, it’s a no-brainer that cables need to be selected to reduce fire hazards. Halogen-free and LSZH cables are particularly notable for emitting much less smoke and no corrosive halogen acids during fire, to keep people, equipment and infrastructure safe. These performance characteristics are not marketing statements, but are closely defined and verified with specific IEC and EN standards and related standards.
Engineers and specifiers use these standards to guarantee that tendered work meets compliance, helps to reduce downtime and safety regulations. This guide explains the tests, what they actually test and how they relate to actual project requirements that are learned from years of cable engineering experience at cable manufacturers such as Hulk Electric.
Why LSZH Compliance Is Defined by Tests, Not Just Marketing Labels
“Low Smoke Zero Halogen” (LSZH), or “Low Smoke Halogen Free (LSHF)” refers to cables that are designed to produce less toxic and corrosive smoke when they are burned. Halogen-free materials help prevent the use of chlorine, fluorine, bromine, and iodine that, when present in the material, cause acidic gases which are detrimental to electronics and respiratory systems.
The actual compliance is found in meeting standardized fire performance tests of the halogen acid gas content, smoke density and flame spread requirements. The term “LSZH” can be confusing if it’s not accompanied by a specific IEC or EN standard. Knowing what these tests mean can help engineers to navigate datasheet claims and produce strong specifications.
Core IEC Standards for Halogen-Free and LSZH Cables
IEC 60754-1 / IEC 60754-2 – Halogen Acid Gas Content and Acidity
These standards measure the quantity and acidity of gases emitted during burning of cable materials. For the halogen acid gas content (typically ≤5mg/g or 0.5% for a halogen-free classification), IEC 60754-1 is used and for the pH (typically ≥4.3) and conductivity (typically ≤10 μS/mm), Part 2 of IEC 60754 applies.
It’s beneficial in areas such as automation and data centers where nearby equipment such as control panels and sensors can suffer from lower levels of acid corrosion. Classified by their compounds, the cables that Hulk offers always comply with these limits.
IEC 61034-1 / IEC 61034-2 – Smoke Density Measurements
Light transmittance through smoke generated by burning cables is measured in this test, which takes place in a 3m³ test chamber. LSZH cables will generally have a transmittance of at least 60% (and often more than 80% for high quality cables) providing increased visibility for evacuation. This can be as much as 70% less smoke than standard PVC cables, which comes in very useful in low space areas, such as tunnels or control rooms.
IEC 60332 (Series) – Flame Spread and Flame Retardancy
IEC 60332-1 tests a single cable with respect to the vertical progression of flame while IEC 60332-3 tests bunched cables. These help to limit the spread of the flame in the risers, corridors and cable trays. These are commonly used in conjunction with the above tests to provide a more comprehensive fire performance for LSZH cables, but circuit integrity is tested under a separate set of standards.
EN/BS Standards and European CPR Requirements
EN 50575 and EN 13501-6 – CPR Euroclass for Reaction to Fire
Cables for permanent installations are classified in accordance with the EU Construction Products Regulation (CPR). The Euroclass B2ca-s1a,d0,a1 means good results for flame spread, heat release, smoke (s1), droplets (d0) and acidity (a1). B2ca or better is required for many modern building projects with LSZH cables.
BS 7211, BS 6724, and Related UK/EN Standards
- BS 7211: Covers non-armoured LSZH cables (300/500 V and 450/750 V).
- BS 6724: Applies to armoured LSZH power cables (600/1000 V).
- These combine IEC tests and electrical and mechanical parameters and are frequently used in conjunction with the EN 50525 series in UK and international projects.
Hulk’s range contains cables which are aligned with these for global compliance.
How “Halogen-Free” Is Defined in Standards and Datasheets
Halogen-free status is based on chemical analysis, and includes limiting the amount of halogens (such as chlorine <0.2%, fluorine <0.1% in some regimes). Seek clear mention of the IEC 60754 findings instead of general statements.
LSZH vs. Low Smoke vs. Flame-Retardant: LSZH requires both low smoke and zero halogen. Always check the complete test suite as flame retardant cables can still have halogens in them.
Project Specifications – How LSZH Standards Show Up on Real Jobs
Common clauses are: All power and control cables in occupied areas shall be LSZH to meet IEC 60754-1/2, IEC 61034-2 (≥60% transmittance), IEC 60332-3 Cat. C and EN 50575 Euroclass B2ca-s1a,d0.
In tunnels or rail: Extra stress on smoke and acid gas of escape routes. These IEC/EN baselines are commonly enhanced by standards for infrastructure projects.
Practical Guidance for Engineers Reading or Writing LSZH Specs
Key Questions to Ask
- Which specific IEC tests (60754, 61034, 60332) are mandated?
- Do we need CPR Euroclass and EN 50575?
- Do country specific standards (BS 7211/6724) or application notes are included?
- Is the spec applicable to the three pillars: gases, smoke and flame?
What to Look for in Manufacturer Datasheets
Ask third party test reports for exact values. These silicone cables are halogen-free and high-temperature, with full traceability, and can be customized to meet the needs of various industries and applications, including food processing and robotics.
The use of the appropriate LSZH cables, according to standards that have been proven, minimizes risk, audit ease and reliability. Tell us your project parameters; we know how to provide you with the customized cables you need in a halogen-free manner.