There is a lot of confusion in the industry regarding claims of low smoke halogen free (LSHF) cables and the materials used in these cables. These LSHF product claims — also known in the industry as low smoke zero halogen (LSZH) — have been in the industry for some time. Of note, these claims are frequently self-certified and the tests used may not be standards based. More importantly, there are some misconceptions about what these tests actually cover, and we’re hoping to offer some clarity with this article.
To better understand LSHF, we need to consider what a halogen is in terms of the Periodic Table of Elements. The five halogen elements found in column 17 are fluorine, chlorine, bromine, astatine and iodine. The three primary elements found in insulation, filler and jacket materials/components are chlorine, bromine and fluorine.
Four predominant wire and cable industry standards — IEC 60754-1, IEC 60754-2, IEC 61249-2 Non-halogenated series, and MIL DTL-24643C Part 3.3 (NEMA WC57)— continue to be the source of some of confusion regarding the halogen content of cable and materials. In particular, incorrect associations are being made, primarily with IEC 60754-1, Test on gases evolved during combustion of materials from cables – Part 1: Determination of the halogen acid gas content, and IEC 60754-2, Test on gases evolved during combustion of materials from cables – Part 2: Determination of acidity (by pH measurement) and conductivity.
These standards do not test for or reference chlorine, bromine or fluorine content levels. Rather, both standards are methods of testing the halogen acid content — via the titration method (IEC 60754-1) and pH & conductivity (IEC 60754-2) — established from the combustion of the tested material. Also, for IEC 60754-2, the minimum pH value of 4.3 and maximum conductivity of 10 μS/mm are described as “recommended performance requirements” as shown in Annex A. This recommendation implies that these requirements are “suggestive” as opposed to “normative” requirements.
The IEC recently developed the LSHF 62821-1, -2 & -3 standard series, Electric Cables – Halogen Free, Low-Smoke, Thermoplastic-Insulated and Sheathed Cables of Rated Voltages Up to and Including 450/750 V. This series is one of the first to provide component material hydrogen free (HF) requirements, complete cable smoke requirements and applicable LSHF cable surface marking.
As a result of the publication of this standard, UL launched two new certification programs: a material Recognition service and an optional cable surface mark program. The material Recognition service uses test methods from IEC 60754-1/-2 and IEC 62821-1/-2 as described under Subject Outline UL 2885, Outline of Investigation for Acid Gas, Acidity and Conductivity of Combusted Material and Assessment of Halogens,” dated 2015-02-12. This service is intended to support suppliers of insulation and jacket compounds, and cable components such as fillers, tapes, wraps, and the like.
For wire and cable manufacturers, UL established a “-HF” and “-LSHF” cable surface Mark designation in accordance with IEC 62821-3 (e.g. Type CMR-LSHF or OFNR-LSHF, TC-LSHF, RHHW-HF, CM-HF, SJO-HF, etc.). We announced this program in an announcement bulletin, “Halogen Free (HF) and Low Smoke Halogen Free (LSHF) Service Offering for Wire and Cable,” dated 2015-02-20.
Should you have any questions or wish to submit your product for testing to this new program, please contact Robert Bellassai at 631-546-2871 or Robert.W.Bellassai@ul.com.