Cable myth-buster: LSF vs LSHF

In the second of a three-part series debunking common cable misconceptions, Paul Bellamy, Managing Director of flex7, looks at LSF and LSHF cables and if it really matters which you use.

“LSF, LSHF? It’s the same stuff.” On behalf of every cable manufacturer – no! That’s like saying a McLaren F1 and a Lada are the same because each has four wheels and gets you from A to B (admittedly, not always the case with the Lada).

Low Smoke & Fume (LSF) cables are made using PVC compounds. Yes, they have a few extras added to inhibit, to some degree, the production of hydrogen chloride emissions in the event of a fire, but that’s all. There are no standards that dictate the level of emissions or the density of the smoke produced when burning, which begs the question: How low is low, exactly?

If your common or garden PVC cable emits, say, 27% hydrogen chloride, is it acceptable for an LSF variant to emit 25%? Should we expect 15% or 10% or even 13.86%? They’re all lower than the 27%, and therein lies the fundamental problem with cables that are marketed as LSF. Without a standard to nail these emission levels down to, LSF cables are like Forrest Gump’s famous box of chocolates: You never know what you’re gonna get. Surely, when it comes to selecting one product over another for its potential safety benefits, a prerequisite should be that it’s abundantly clear what those benefits are?

On the other hand, Low Smoke Halogen Free cables (LSHF, aka LS0H, LSZH) contain no PVC and that means hydrogen chloride emissions during the burning process are virtually zero. A cable cannot be marketed as being LSHF if, during testing, it is found to emit more than 0.5% hydrogen chloride. In addition, smoke production should be low and result in visibility not being reduced by more than 40%. Zero hydrogen chloride and vastly improved visibility are key properties to safer evacuation from a burning building; the benefits of installing LSHF cable over PVC or LSF are clear.

In hindsight, perhaps the McLaren/Lada comparison was a poor choice, as they look nothing like each other. That’s probably where a lot of the confusion lies with LSF and LSHF cables. The acronyms commonly used are almost identical, and one type of cable looks very similar to another, especially if the only difference is the chemical composition of the ‘plasticky’ stuff it’s covered in. However, where comparing these two cars does work is when it comes to performance, as they’re obviously poles apart on that front – much the same as LSF and LSHF cables.

flex7.co.uk

This article appeared in Electrotechnical News March/April 2026 edition – read it here

Part three of the cable myth-buster series will focus on CPR – read it in the May/June issue of Electrotechnical News. Part one looked at BASEC approval – read it here.