Myth – LSF and LSHF Cable are the same thing

The world of cable is, at best, convoluted and, at worst, a massive can of writhing, slippery worms. It’s full of obscure acronyms and complicated standards, so it’s not surprising that, over time, a number of misconceptions have woven their way into the fabric of this vitally important sector of the construction industry.

Part 2  in our series of cable myths focuses on LSF and LSHF and if it really matters which you use:

On behalf of every cable manufacturer out there, no, no and no again. That’s like saying a McLaren F1 and a Lada are the same because each has four wheels, get you from A to B (admittedly, not always the case with the Lada) and they’re both “cars”.

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 (it might be a bit more, it might be a bit less), is it acceptable for an LSF variant to emit 25%? Should we expect 15% or 10% or 13.86% (if we want to get a bit silly about it)? They’re all lower than the 27% I mentioned to start with. And thereby 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 – other initialisms are available on request) 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 – an undeniable fact. The benefits of installing LSHF cable over PVC or LSF are clear for all to see.

In hindsight, perhaps the McLaren/Lada comparison was a poor choice as they look nothing like each other. And to be fair, that’s probably where a lot of the confusion lies with LSF & LSHF cable. The initialisms 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 & LSHF cable.