Quick answer: If an LSZH grade runs well on your building wire, do not assume it will pass a rolling-stock or shipboard order. The five main LSZH cable compound uses — building wire, data cable, rail, marine and the sheath on medium-voltage cable — are governed by different standards, and the flame test is rarely where they differ. Smoke toxicity, oil resistance and wall thickness are where a good general grade fails.
We get asked for “an LSZH compound” as if it were one material. It is a family. The halogen-free, low-smoke part is common to all of them; almost everything else — polymer base, crosslinked or not, filler type, mechanical targets — changes with where the cable ends up.
Five uses, side by side
| Use | Governing standard(s) | What is actually hard | What changes in the compound |
|---|---|---|---|
| Building wire (EU) | CPR Euroclass via EN 50575; UK armoured cable to BS 6724 | Reaching B2ca or Cca on the finished cable | General-purpose thermoplastic sheath; UK BS 6724 uses LTS 1 to BS 7655-6.1 |
| Data cable (LAN) | CPR Cca / Dca; ISO/IEC 11801 Class E, TIA-568.2-D for Cat 6 performance | Thin jacket, high line speed, surface finish | Finer filler, tighter dispersion, better melt flow |
| Rail rolling stock | EN 45545-2, cable requirement sets R15 / R16, hazard levels HL1–HL3 | Smoke ≥70 % transmission and toxicity at HL3 | Smoke and toxicity become design targets, not side effects |
| Marine & offshore | IEC 60092-360 sheath types SHF1 / SHF2; NEK 606 SHF Mud offshore | Oil and drilling-mud resistance | Polymer base changes; SHF2 and mud grades are usually crosslinked |
| MV / HV sheath | Cable standard for the installation; LSZH only where enclosed spaces demand it | Mechanical toughness on large diameters | Sheath only — insulation stays XLPE |
Two things stand out from that table. First, every row has halogen-free and low-smoke in common, which is why one grade gets over-sold across all five. Second, the “what is hard” column is different in every row — and none of them says “flame propagation”.
Building wire: where most of the volume is
For fixed installation in EU buildings, the cable carries a Euroclass under the Construction Products Regulation, and B2ca or Cca is the common floor for public buildings. The class belongs to the cable construction, not the compound — which is why asking for a compound Euroclass goes nowhere, as covered in LSZH cable compound certification.
In the UK, the workhorse is the armoured 600/1000 V cable to BS 6724: XLPE or EPR insulation, wire armour, and an LSZH outer sheath specified as LTS 1 under BS 7655-6.1. These go into underground transit, airports, hospitals and high-rise buildings. For the compound, this is the forgiving end of the family: moderate wall thickness, a standard general-purpose grade built on magnesium hydroxide flame retardant or ATH, and mechanical targets most competent producers hit.
Data cable: the thin-wall problem
A Cat 6 jacket is thin, and it runs fast. Both of those punish exactly what an LSZH compound is weakest at. With 55–65 % mineral filler in a thin wall, a coarse particle or an undispersed cluster is no longer a small defect — it is a surface bump, a weak point on bending, or a spark-test fault.
So the data-cable grade usually differs from the building-wire grade not in its flame package but in filler particle size, surface treatment and melt flow. If you are running LAN cable on a grade qualified for power cable sheathing, surface complaints and line-speed limits are the most likely symptoms, not a burn failure. The processing side of this — feed order, dispersion, why lots vary — is in LSZH cable compound production process.
The Cat 6 electrical performance itself (ISO/IEC 11801 Class E, TIA-568.2-D) is a matter of pair design, not the jacket compound. Do not let anyone sell you a jacket grade as the reason a cable meets Category 6.
Rail: the toxicity number, not the flame number
EN 45545-2 is the standard that most often catches out a cable maker moving from building wire into rolling stock. Cable requirements sit in two requirement sets, R15 and R16, graded by hazard level HL1 to HL3 according to the operation category — tunnels, elevated sections and so on.
The tests will look familiar: EN 60332-1-2 for single-cable flame propagation, EN 60332-3-24 for larger cables of 12 mm and up, EN 61034-2 for smoke, EN 60754 for acid gas, and EN 50305 for toxicity. The limits are what change. Smoke transmission has to reach at least 50 % at HL2 and 70 % at HL3, and the toxicity index has to stay at or below 10 at HL2 and 6 at HL3.
Compare that with the general IEC 61034 expectation of 60 % light transmittance that most building-wire grades are designed around. A compound that passes comfortably at 64 % is a good building-wire compound and an HL3 failure. The smoke density test article explains why the same test gives different verdicts under different standards.
One shortcut worth knowing: cables that meet the fire requirements of the railway cable standards EN 50264, EN 50306 or EN 50382 are treated as meeting R15 and R16 for the corresponding hazard level without further testing. If your customer’s cable is built to one of those, qualify to it directly.
Marine and offshore: oil resistance is a polymer decision
On ships and offshore units, IEC 60092-360 governs the insulating and sheathing materials, and the halogen-free sheath types split by oil resistance. SHF1 is tested in ASTM No. 2 oil for 4 hours at 70 °C. SHF2 is tested in IRM 902 oil for 24 hours at 100 °C — a much harsher exposure. For offshore platforms, NEK 606 adds mud-resistant sheaths designated SHF Mud.
No amount of flame retardant helps here. Oil and mud resistance come from the polymer matrix, which is why SHF2 and mud-resistant grades are typically crosslinked and built on more polar polymer systems — one published route combines nitrile rubber with ethylene methyl acrylate copolymer to meet both SHF2 and NEK 606. That is a very different compound from a thermoplastic building-wire sheath, even though both are called LSZH.
MV and HV: LSZH is only ever a sheath question
We get enquiries for “LSZH compound for high-voltage cable” and the honest answer is usually a clarification. The insulation on MV and HV cable is XLPE; that is not a flame retardant product and not something we supply. The LSZH question applies only to the outer sheath, and only where the cable runs through enclosed or occupied spaces — tunnels, metro systems, building risers. Buried and outdoor runs are usually better served by a PE sheath, and if the run is outdoors in any case, weathering becomes the next problem, covered in UV resistant LSZH compound.
A metro order that failed on 6 percentage points
A cable maker in Poland with a well-run building-wire business took a first order for metro rolling-stock control cable, HL3. They used the LSZH sheath grade they had run for years on Cca building cable, because it had never given them a problem.
It passed EN 60332-1-2 easily. The smoke test came back at 64 % transmission. Under IEC 61034 for their building cable that is a comfortable pass. Under EN 45545-2 HL3 it is a fail by six points.
The fix was not more flame retardant. It was a different grade with the smoke and toxicity package designed in from the start, rebalanced toward MDH, with the whole construction re-tested. From the failed report to a passing one took nine weeks, and they lost their first slot at the test house, which cost them more than the compound did. Their technical manager told me afterwards that the mistake was treating “LSZH” as a specification. I agree, and I have made the same assumption on their behalf before.
What we would advise
If you make building wire and are moving into rail or marine: treat it as a new qualification, not a line extension. Get the target standard, hazard level or sheath type written down before you request samples, and budget for a full re-test of the construction.
If you make LAN cable: ask specifically for a thin-wall grade and qualify it at your real line speed. A grade that looks identical on the datasheet can behave very differently at speed.
If you need an offshore NEK 606 mud-resistant sheath: we may not be your fastest route. It is a specialist crosslinked grade with relatively few qualified producers, and we would rather tell you upfront whether our partner factories have a qualified grade than promise one and learn during qualification.
If you just need LSZH for general building cable: do not over-specify. A rail- or marine-grade compound costs more and brings nothing to a riser cable. Our LSZH cable compound range is organised by use for exactly this reason.
FAQ
What are the main LSZH cable compound uses?
Building wire and power cable for fixed installations, data and LAN cable, rail rolling-stock cable, marine and offshore cable, and the outer sheath on medium- and high-voltage cable in enclosed spaces. They share the halogen-free, low-smoke principle but are specified to different standards and usually need different grades.
Can one LSZH compound cover building wire and rail?
Sometimes for HL1 or HL2, rarely for HL3. EN 45545-2 at HL3 asks for at least 70 % smoke transmission and a toxicity index of 6 or lower, which is tighter than the 60 % most building-wire grades are designed around. Test the actual construction before committing.
What is the difference between SHF1 and SHF2?
Both are halogen-free sheath types under IEC 60092-360. The key difference is oil resistance: SHF1 is tested in ASTM No. 2 oil for 4 hours at 70 °C, SHF2 in IRM 902 oil for 24 hours at 100 °C. SHF2 is the harsher requirement and usually needs a crosslinked, more polar polymer base.
Is LSZH required for data cables?
Not universally, but in the EU permanently installed data cable needs a CPR Euroclass, and many projects specify Cca or Dca with halogen-free requirements. The practical challenge is thin-wall extrusion, which favours finer, better-dispersed filler. The fibre side of the same question is covered in flame retardant fiber optic cable.
Do you supply compound for all five uses?
Building wire, data cable and general sheathing grades, yes, as finished flame retardant compound or as halogen-free flame retardant packages for compounders. Rail and marine grades depend on which partner factory holds a qualified grade for your target; we confirm that before quoting rather than after. We do not supply MV or HV insulation.
What should I send with an enquiry?
The use, the governing standard and level (Euroclass, HL, SHF type), the cable construction and wall thickness, your line speed, and your elongation minimum. The standards map for the wider cable picture is on our flame retardant for wire and cable page.
Final thoughts
“LSZH” tells you what a cable will not do in a fire: release halogen acid or dense smoke. It says nothing about oil, mud, thin walls or toxicity limits, and those are where orders fail. Name the use and the standard before the material, and the grade selection mostly makes itself. Send us the cable, the standard and the level, and we will tell you which grade fits — and, when it is a specialist grade our partner factories have not qualified, we will say that too.
—— Rectivas Materials 团队 技术工程师老陈