LSF vs LSHF (LSZH) - There is a Difference!

When comparing LSF and LSHF (LSZH) cables, it becomes clear that specific performance characteristics are crucial for safely navigating fire risks in populated spaces. LSHF cables, made up of halogen-free compounds, act as effective fire retardants while emitting less than 0.5% hydrogen chloride gas and minimal smoke when burned. The light grey smoke produced ensures better visibility for escape routes during emergencies, drastically enhancing the chances of safe exit from crowded areas. In contrast, LSF cables, though flexible and less costly, still emit a dangerous level of toxic gases.

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• These cables are ideal for airports, railway stations, computer rooms, and data centers, where fire safety is paramount and escape routes may be limited.
• With an HCL gas emission of less than 0.5%, they contribute to a safer environment in case of fire.
• Low smoke generation keeps evacuation routes and signage visible when a fire occurs.

PVC vs LSF vs LSZH Conclusion

While LSF cables offer flexibility and lower cost compared to PVC cables, they still pose risks through toxic gas emissions when burned. In contrast, LSHF cables may come at a higher price and reduced flexibility but deliver significantly lower toxic smoke and gas emissions. For high-risk areas where evacuation may be difficult, LSHF cables are strongly recommended. For locations with low risk and easy evacuations, PVC cables remain a feasible option.

Despite intrinsic differences in the quantity of toxic fumes and smoke generated, all cable types can pass the CPR test to class Eca.

What about CPR?

Most cables meant for permanent installation in residential and commercial buildings now fall under the Construction Products Regulation (CPR), elaborated in BS EN. This became a legal requirement in July. This standard addresses fire spread and heat release rather than gas toxicity.

The Euroclasses

The regulation categorizes products into seven classes, but typically only five apply to cables. Basic vertical flame tests designate lower classes Fca and Eca. A high flammability level results in classification as Class Fca (in-house testing is allowed). However, Class Eca compliance must be verified by a certified Notified Body.

During the test, a single cable approximately 60 cm long is secured in a vertical position with two clamps, and a flame is applied at the bottom for 60 seconds (or 120 seconds for cables wider than 25 mm). The test is successful if the flame extinguishes post-application, resulting in less than 425 mm of damaged cable. The duration of cable burning before extinguishing is not evaluated.

Great! All I need is CPR class Eca compliant cables, and I won't have to worry about materials!

If only it were that simple!

The 18th edition of BS recognizes the necessity for cables to meet CPR requirements while carrying a Euroclass for fire performance. Nevertheless, it does not restrict the usage of cables that release toxic fumes during a fire. It's imperative for specifiers and installers to choose cables suited for the specific fire risk profiles of their projects.

Part B of The Building Regulations provides further advice.

The key danger during the early stages of a fire is not the flames but the smoke and toxic gases formed, often causing the majority of casualties and obscuring escape routes. Thus, precautions must limit smoke and fume spread to ensure safe evacuation.

So, should I simply opt for the highest CPR class?

Choosing a high-level CPR classification may be economically challenging for contractors, who might find such cables rare or unavailable. Compliance with higher classifications can be costly for manufacturers due to extended R&D efforts and may not be feasible for many cable types.

Moreover, cables designed to meet these higher CPR standards may compromise their electrical or data performance, affecting installation methods and system efficiency.

Lower CPR classifications focus on fire spread, not toxic gas and smoke emissions. To address smoke concerns, Low Smoke Halogen Free (LSHF) cables should be prioritized, but beware, as terminology can be misleading.

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