There is a lot of confusion in the industry regarding claims, mostly self-certified, of low smoke halogen free cables and the materials used in them.
Product claims about low smoke halogen free (LSHF) – also known by the industry as low smoke zero halogen (LSZH) – have been with us for some time now. Of note, these claims are frequently self-certified, and tests used may not be standards-based. More importantly, there are some misconceptions about what some tests cover, which this article aims to clarify.
LSHF products, which originated in Europe and the United States in the 1970s, were used in the early 1980s in applications such as the London Underground, the United Kingdom’s Royal Navy and North Sea offshore oil drilling platforms. LSHF cables were installed in confined spaces where the toxicity and corrosivity of the smoke generated in a fire would be particularly problematic. The adoption of LSHF cable products has been slow in the United States, but that has changed due to some high-profile fires. A key example is the Jan. 12, 2016 L’Enfant Plaza incident[i] in Washington DC, where an electrical malfunction fire filled a tunnel with smoke, killing one person and injuring others.
LSHF cable products have traditionally been found in the power and control categories but have branched out to categories including data/telecom cables, fiber optic cables and appliance wire and cable. They are being used in more locations than the traditional confined spaces (tunnels, subways, ships, submarines and mines), and are now also found in hospitals and data centers. In response, UL will be proposing the optional HF and LSHF Marking for the 2020 National Electrical Code (NEC) revision cycle.
Asia and South America are also adopting LSHF wire and cable, which has been the EU approach to cable standards. In a global economy, manufacturers now have access to a standards-based LSHF cable designation and cable designers can produce one design that can be sold and applied around the world.
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 the confusion regarding the halogen content of cable and materials. There is still an incorrect association, 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 fluorine, chlorine, bromine and iodine content levels; they are methods to test the halogen acid content – via titration method in the case of IEC 60754-1 and pH & conductivity for 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), 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 Halogen Free (HF) material Recognition service and an optional HF and LSHF cable surface mark program.
The material Recognition service uses an Ion-Chromatography test method from IEC 60754-3 as described under the newly published Subject Outline UL 2885, “Outline of Investigation for Acid Gas, Acidity and Conductivity of Combusted Material and Assessment of Halogens,” dated 2018-11-27. This service is geared to support suppliers of insulation and jacket compounds, and cable components such as fillers, tapes, wraps, and the like. It can be summarized as follows:
IEC 60754-3. Under the UL 2885 standard, combustible materials are evaluated for the maximum amount of the following halides; fluorine, chlorine, bromine and iodine. The maximum allowable amount of these halides is limited to 1000 Parts Per Million (ppm). Combustible materials (insulation, jacket, fillers, tapes, etc.) evaluated under this service/standard(s) would not make claims or assertions to the halogen content of the material(s) and are not appropriate for use in validating cable products or their material components as non-halogen, zero halogen, halogen-free, low halogen or LSZH.
Under the UL 2885 standard, combustible materials are evaluated for halogen content. Materials evaluated under this standard will allow for the HF material Recognition designation for any combustible compound/component in a finished cable. Suppliers of insulation and jacket compounds and cable components may choose to obtain a material Recognition for any one or more of the above standards.
For wire and cable manufacturers, UL established a -HF and -LSHF cable surface Mark designation in accordance to IEC 62821-3 (e.g. Type CMR-LSHF or OFNR-LSHF, TC-LSHF, RHHW-HF, CM-HF, SJO-HF, etc.). UL 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.
Under the -HF and -LSHF cable program, all combustible materials (insulation, jacket, fillers, tapes, wraps, shields, etc.) must first be recognized under UL’s material Recognition Program as per UL 2885 (described above) or tested individually by the cable manufacturer. The cable manufacturer would be authorized to use these HF Recognized materials in order to apply the -HF and -LSHF optional cable surface mark.
Under the optional cable surface mark program, no reference is permitted, within the UL print legend surface print, regarding non-halogen, non-halogenated, zero halogen, low halogen or LSZH or reference material provided by the cable manufacturer as these designations are not covered in the IEC 62821-3 standard.
Currently, UL has certified many wire and cable companies to mark certain cable constructions as HF and LSHF and numerous suppliers of HF compound material to the wire and cable industry.
Robert Bellassai will present “Low smoke halogen Free (LSHF) – what does it mean?” at 6pm on the 6th of March 2019, at AMI’s upcoming “Cables 2019” conference, which takes place at the Maritim Hotel in Düsseldorf.
For more information or to submit a product
for testing to this new program, please contact Robert Bellassai at UL’s office
in Melville, New York, tel. 631-546-2871, Robert.W.Bellassai@ul.com or
David Cavassa in France, tel. +33 666 013 192, David.Cavassa@ul.com.
[i] “1 dead, dozens hurt after Metro car fills with smoke”, by Paul Duggan, Peter Hermann and Julie Zauzmer, January 13, 2015, Washington Post
Image source: Courtesy of UL
Read more about UL here