What LSZH means
LSZH stands for low smoke zero halogen. Other spellings for the same family include LS0H, LSOH, LSHF and HFFR (halogen-free flame-retardant). The idea is simple: when a cable burns in an enclosed space, the sheath should give off less dense smoke and no significant halogen acid gas, so that people can see escape routes and electronics are not corroded by acid fumes. A standard PVC compound contains chlorine; in a fire it releases hydrogen chloride, which forms hydrochloric acid with moisture and produces thick black smoke.
An LSZH compound replaces PVC with a polyolefin base and mineral fillers that release water when heated, which slows burning and keeps the smoke lighter. It does not mean the cable does not burn or that it produces no smoke. Every cable sheath burns given enough heat. LSZH is a measured reduction, defined by three test methods, and its flame behaviour is a separate question.
The three tests behind the label
| Test | What it measures | Commonly specified limit |
|---|---|---|
| IEC 61034 (smoke density) | Light transmittance through the smoke released by a burning cable sample in a closed test chamber | Light transmittance of at least 60% |
| IEC 60754-1 (halogen acid gas) | Amount of halogen acid gas released from the compound | Not more than 0.5% |
| IEC 60754-2 (acidity and conductivity) | pH and conductivity of the gases dissolved in water | pH of at least 4.3; conductivity not more than 10 uS/mm |
Those limits are the values commonly specified for LSZH in IEC-based project specifications and UK standards; your project specification or the cable standard sets the limit that applies. The desk asks for all three test reports on the sheath compound or the finished cable, with the report date and the construction tested. The detailed method behind each test is in the IEC 61034 and IEC 60754 article.
LSZH is not the same as flame-retardant or fire-resistant
Three properties are often confused on enquiries, and each has its own test:
- Smoke and acid gas: IEC 61034 and IEC 60754, as above. This is what LSZH means.
- Flame spread: IEC 60332-1-2 for a single cable and IEC 60332-3 for bunched cables. A cable can be LSZH and still fail the bunched test if the compound or construction is weak, so ask for flame-retardant to IEC 60332-1-2 or 60332-3 per test report.
- Circuit integrity: IEC 60331, BS 6387 CWZ or BS 8519. This is about keeping a circuit working during a fire, and it needs a fire barrier such as mica tape. LSZH alone does not provide it.
The fire performance classes page sets these side by side, and the fire-resistant cables page shows a reference construction with mica tape, XLPE insulation and an LSZH outer sheath.
Where LSZH is required
LSZH is usually requested where people gather or where escape is slow: tunnels, metros, hospitals, airports, high-rise buildings, data centres and ships. In the UK, BS 6724 covers LSZH armoured cable, the counterpart of the PVC-sheathed BS 5467 type, and BS 7211 covers LSZH wiring cable such as the 6242B twin and earth, the counterpart of BS 6004 PVC. Indoor fibre cables are commonly offered with LSZH jackets, as on our indoor fibre cables page.
In the EU, cable for permanent installation in buildings falls under the CPR and EN 50575. The CPR class on the Declaration of Performance can carry additional classes for smoke (s1, s2, s3) and acidity (a1, a2, a3). A national installation rule or a project specification may then require, for example, s1 and a1 for escape routes. The CPR class is declared on the DoP for the finished cable; it is not a property of the compound. The CPR classes article explains the letters.
Where LSZH is not required, PVC is still common because it is easier to process, more resistant to some oils, and usually cheaper. The LSZH vs PVC article covers that choice market by market.
Practical differences buyers notice
LSZH compounds behave differently from PVC during production and installation, and those differences show up on the order:
- Mechanical: heavily filled LSZH compounds can be stiffer and less resistant to abrasion than PVC. Pulling lubricants and installation temperature should follow the cable maker's datasheet.
- Water and oil: some LSZH compounds absorb more water or swell in oil. For wet or oily locations, ask the plant which compound grade is used and what the datasheet allows.
- Print and colour: LSZH sheaths are often supplied in black, grey or a project colour, and the print should state the standard and the LSZH designation exactly as the type test report does.
- Lead time: LSZH compound may not be stocked for every colour, so production slots can depend on compound supply. Lead time is confirmed in writing for each order.
Price is the other difference buyers notice. LSZH compound generally costs more than general-purpose PVC, and because a power cable sheath is thick, the compound share of the price per metre rises with it. Copper still dominates the cost of most power cable, but on small multicore, control and data cables the sheath compound is a larger part of the total, so the gap between a PVC quote and an LSZH quote is wider there. Compare quotes only when both name the same compound grade and both carry the same test reports; a cheaper 'LSZH' offer without IEC 60754 results is not the same product. Packing, drum lengths and minimum quantities per size follow the usual ranges on the MOQ and lead time page, confirmed in writing for each order.
How the desk checks an LSZH claim
- Match the construction: the test reports must cover the same compound and a comparable construction to the cable being ordered.
- Read all three results: IEC 61034, IEC 60754-1 and IEC 60754-2, with values, not just 'pass'.
- Separate flame and fire: check IEC 60332 and, where required, IEC 60331 or BS 6387 reports on their own.
- Check the market document: for the EU, the DoP and CE label for the CPR class; for the UK, a BASEC approval held by the partner plant for that construction where the project asks for it, checked in the certifier's public database per order.
- Verify on the drum: sheath print, colour and length marks at pre-shipment inspection.
To start, list the cables, the standard and the LSZH requirement on the quote form.