LSZH Cable Labels: How to Mark Wires in Low Smoke Zero Halogen Environments

Low Smoke Zero Halogen (LSZH) describes materials that have two critical fire safety properties. First, they produce minimal smoke when exposed to fire, helping to maintain visibility during evacuations. Second, they contain no halogen elements such as fluorine, chlorine, bromine, or iodine, which means they do not release corrosive or toxic hydrogen halide gases when burning.

The importance of these properties becomes clear when you consider the conditions during a fire in a confined space. According to fire safety research, smoke inhalation accounts for the majority of fire-related fatalities. In railway carriages or underground stations, maintaining visibility and breathable air for even a few additional minutes can be the difference between safe evacuation and tragedy.

For a deeper understanding of how to select the right cable and wire labels for UK engineering projects, including material considerations, our comprehensive guide provides detailed selection criteria.

LSZH requirements extend far beyond just the cables themselves. Any component attached to those cables, including wire labels, cable tags, and identification markers, must meet the same fire safety standards. This ensures that the entire installation maintains its safety rating rather than being compromised by non-compliant labelling.

The London Underground provides a particularly stringent example. Following the King's Cross fire in 1987, which claimed 31 lives, Transport for London developed the LUL 1-085 standard specifically for materials used on the network. This standard applies to all components, including cable markers and wire markers used throughout stations and tunnels.

Understanding the relevant standards helps ensure your cable labelling meets project specifications. Different industries and regions may reference different standards, though they share similar underlying principles regarding smoke emission and halogen content.

EN 45545-2: Railway Fire Safety

This European standard specifies fire protection requirements for materials used on railway vehicles. It categorises materials into different hazard levels (HL1, HL2, HL3) based on the operating category of the vehicle. Cable labels used in rail applications typically need to meet the R22 or R23 requirement sets, which define acceptable smoke density and toxicity levels.

LUL 1-085: London Underground

Transport for London's specification goes beyond EN 45545 in certain areas, reflecting the unique challenges of the underground environment. Materials must pass specific tests for oxygen index, smoke emission, and toxic fume emission as defined in BS 6853. Products approved for LUL 1-085 can be confidently used in demanding public transport applications.

IMO FTPC: Marine Applications

The International Maritime Organization's Fire Test Procedures Code governs materials used on ships. Parts 2 and 5 cover smoke and toxicity (Part 2) and surface spread of flame (Part 5) requirements. Offshore installations often reference these standards alongside industry-specific requirements.

UL 94 V-0: Flammability Rating

While not specific to LSZH, the UL 94 vertical burn test provides a widely recognised flammability classification. Materials rated V-0 self-extinguish within 10 seconds after removal of the flame source. This rating is often specified alongside LSZH requirements for comprehensive fire safety.

For more information on cable labelling standards including ANSI/TIA requirements for data centres, see our guide to ANSI TIA 606-B cable labelling standards.

Choosing compliant cable labels involves more than simply picking a product labelled "LSZH". You need to verify that the specific product has been tested against the standards required for your project, and that it will perform reliably in your operating environment.

1. 1

   Verify Test Certifications

   Request test certificates or datasheets showing compliance with the specific standards required. A reputable manufacturer will provide documentation showing their labels have been independently tested to EN 45545-2, LUL 1-085, or other relevant standards.

2. 2

   Consider Operating Environment

   LSZH compliance is just one requirement. Labels may also need UV stability for outdoor applications, chemical resistance for industrial environments, or extreme temperature tolerance. Ensure the product meets all environmental requirements, not just fire safety.

3. 3

   Check Print Durability

   The label material may be LSZH compliant, but what about the print? Thermal transfer printing with appropriate ribbons ensures text remains legible throughout the label's lifespan. Poorly printed labels can become unreadable, defeating the purpose of cable identification.

4. 4

   Assess Application Method

   Consider whether tie-on labels, or heatshrink markers best suit your cable types and installation conditions. The attachment method should secure labels firmly without damaging cable insulation or compromising LSZH properties.

Our guide to labelling terminated wires covers the practical aspects of applying different label types in various installation scenarios.

Silver Fox® developed Fox-Flo® specifically for environments where LSZH compliance is mandatory. The material is manufactured in-house to our own specification, giving complete control over the formulation and ensuring consistent quality across every batch.

Fox-Flo® cable labels operate across a temperature range of -40°C to +100°C, making them suitable for everything from cold storage facilities to engine compartments. The material has also been tested for resistance to H2S sour gas exposure, salt mist spray, and a range of chemicals and solvents commonly encountered in industrial environments.

Why UV Stability Matters

Many LSZH applications are outdoors or in areas with significant UV exposure. Trackside installations, offshore platforms, and station platforms all expose labels to sunlight. Fox-Flo® has been tested to ISO 4982 Part 3 for 8,000 hours of accelerated UV weathering, equivalent to 12-15 years in a Northern European climate. This ensures labels remain legible throughout their service life.

For applications requiring heatshrink markers rather than tie-on labels, Silver Fox® also offers Legend™ LSZH Heatshrink in continuous roll format, tested to the same EN 45545-2 and LUL 1-085 standards.

Having compliant label material is only part of the solution. The printing system must produce durable, legible text that withstands the same environmental conditions as the label itself. Fox-in-a-Box® is an all-in-one thermal printing system designed specifically for industrial cable labelling, including LSZH applications.

The system operates on a "one software, one printer, one ribbon" principle. The Labacus Innovator® software handles label design with features including barcode generation, sequential numbering, and data import from spreadsheets. The same Fox-in-a-Box® printer and TSR3/300 thermal transfer ribbon work across the entire range of Silver Fox® thermal labels, whether LSZH tie-ons, heatshrink, or standard PVC labels.

Software Features for Efficient Cable Labelling

Labacus Innovator® includes templates for common label formats and allows custom designs for specific requirements. Engineers can import cable schedules directly, generate barcodes or QR codes for asset tracking, and print batch runs efficiently. The software is available in Basic, Advanced, and Professional tiers to match different project requirements.

For data centre applications, see our detailed guide on how to label ethernet cables, network cables, and data centres.

How do I label wires and cables in LSZH environments?

Start by selecting cable labels that are certified to the specific LSZH standard required for your project, such as EN 45545-2 for rail or LUL 1-085 for London Underground work. Use a thermal transfer printing system with appropriate ribbons to ensure print durability. Apply labels according to your project's labelling schedule, positioning them for visibility during maintenance while ensuring secure attachment with cable ties or integrated tie features.

Can I use standard wire markers in LSZH-required areas?

No. Standard PVC-based wire markers are not LSZH compliant and will compromise the fire safety rating of the entire installation. Using non-compliant cable tags in areas where LSZH is mandated can result in failed inspections, project delays, and potential liability issues. Always verify label compliance before installation.

What is the difference between LSZH and LSOH cable labels?

These terms are essentially interchangeable. LSZH (Low Smoke Zero Halogen) and LSOH (Low Smoke Zero Halogen) refer to the same material properties. Some regions or industries prefer one term over the other, but both describe materials that produce minimal smoke and contain no halogen elements.

Are LSZH labels more expensive than standard labels?

LSZH labels typically cost more than standard PVC labels due to the specialised material formulation and testing requirements. However, the cost difference is minor compared to the overall project budget, and using non-compliant labels would require complete replacement if identified during inspection. The additional cost provides peace of mind and ensures project compliance.

How long do LSZH cable labels last outdoors?

This depends on the specific product and environmental conditions. Fox-Flo® labels have been tested for 8,000 hours of accelerated UV exposure, which corresponds to approximately 12-15 years in a Northern European climate. Products from other manufacturers may have different performance characteristics, so always check the UV stability rating in the product specifications.