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Modern railway systems demand robust fire and smoke protection. The EN 45545 standard unifies strict European fire-safety rules for rail vehicles, requiring all cable assemblies and components to limit flame spread, smoke density, and toxic gas emissions. In practice, every cable harness and connector on a train – even an HDMI cable for passenger displays – must use fire-resistant, low-smoke materials. Cable assemblies must therefore be designed and tested to comply with EN45545’s flame retardancy, smoke opacity, and toxicity criteria.
Understanding EN45545: The Railway Fire-Safety Standard
EN45545-1 through EN45545-4 cover fire protection for rolling stock. Part 2 is key for materials: it defines “Requirement Sets” (Rxx) and Hazard Levels (HL1–HL3) based on the train’s operating environment. For example, internal components must meet the R22 set (flammability, smoke and toxicity limits) while exterior parts follow R23. Higher hazard levels (HL3) apply to trains in long tunnels or with sleeper cars, imposing more stringent tests. In effect, any new cable or connector is categorised (e.g. EL1A internal cable) and must pass the relevant R-set tests at the assigned HL.
Fire Resistance: Flame-Retardant Materials and Cables
Cable insulation and jacket are the first line of defence. EN45545-compliant cables use flame-retardant, self-extinguishing materials. Railway cables are halogen-free to avoid spreading toxic fumes and flames. They typically feature a flame-retardant jacketing and insulation rated to UL94 V-0 or better. For instance, specialised rail cable products are marketed as halogen-free, continuously flexible, and “flame retardant and self-extinguishing”. These cables pass fire-propagation tests (IEC 60332), so a short circuit or ignition won’t sustain a fire. Key cable characteristics include:
- Halogen-free, flame-retardant sheath – prevents burning droplets and toxic acid gases.
- Self-extinguishing design – cable stops burning once the ignition source is removed.
- High oxygen index (LOI) – material requires higher than ~32% oxygen to burn, as EN45545 often requires.
- Mechanical robustness – flexibility, abrasion resistance, and UV/oil resistance for the rail environment.
Together, these features ensure the cable itself does not fuel a fire.
Smoke and Toxicity: Meeting Critical Safety Requirements
EN45545 also sets strict limits on smoke density and toxic gas generation. In a fire, cable materials must not emit excessive smoke that would obscure vision or hamper evacuation. Low-smoke (LSOH) compounds are used so that optical density (Ds) stays below the EN45545 threshold. Likewise, halogen-free materials prevent the generation of acid gases (HCl, HF) and other toxins. EN45545-2 Annexe C defines a Conventional Toxicity Index (CIT) to measure harmful combustion products. Key safety requirements include:
- Smoke density limits: To keep smoke output low, cables are tested for smoke opacity (EN45545 Test O3).
- Toxic gas limits: combustion gases (HCl, CO, NOx, etc.) are measured (CIT) and must remain below the prescribed level.
- Halogen-free construction: avoids corrosive/harmful fumes in a fire, ensuring compliance with EN45545 toxicity classes.
By meeting these requirements, cable assemblies minimise the danger of smoke and poisons during an onboard fire.
Connectors and Components for EN45545 Compliance
Not only does the cable matter – all connectors, plugs, glands and assemblies must also meet EN45545. Small electrical parts (like connector housings) fall under requirement R26, which mandates V-0 rated materials in all hazard levels. Manufacturers use special UL94 V-0 polyamide or other self-extinguishing plastics for connectors and terminals. For example, WAGO’s rail connectors use PA6.6 V0 insulators to satisfy EN45545 R26. Ruggedised data/connectors are also available: a reinforced HDMI connector system, for instance, is explicitly built with a fire-retardant, low-smoke design that meets EN45545. Cable glands, potting compounds and mounting hardware should likewise be chosen for EN45545 compliance. In short, every element of the harness – from signal plug to cable – must be fire-safe by design.
Testing and Certification for EN45545 Compliance
Compliance is proven by standardised testing. Cable assemblies are sent to accredited labs for the EN45545-2 battery of tests. Key test metrics include:
- Oxygen Index (LOI) – measures the minimum oxygen needed to sustain burning.
- Smoke density (Ds) – evaluates how much smoke the material emits under fire.
- Toxic gas analysis (CIT) – quantifies harmful gases from combustion.
- Flame spread and drips – ensures no sustained flame propagation or falling fire droplets.
Each test result is compared against the R-set limits for the application’s hazard level. Only assemblies that pass all relevant criteria earn EN45545 certification. Manufacturers document compliance with official test reports (noting R-sets like R15, R22, etc.).
By following these processes, designers and suppliers ensure that every cable assembly (and its connectors) is fully EN45545-certified before installation.
Romtronic: Your EN45545-Compliant Cable Assembly Partner
Meeting EN45545 is a top priority for Romtronic. As a professional cable assembly and wire-harness manufacturer with ISO 9001 and IATF 16949-certified facilities, Romtronic delivers high-quality, customised wiring solutions worldwide. We incorporate EN45545-safe materials (halogen-free, V-0 polymers, etc.) into our designs and conduct rigorous in-house and third-party testing. Our engineers work closely with clients to select the right flame-retardant cables and connectors for each rail application (including HDMI and other data/video lines). In short, Romtronic offers fully EN45545-compliant cable assemblies built to last in demanding railway environments, backed by proven quality control and reliability.
Sam Wu is the Marketing Manager at Romtronic, holding a degree in Mechatronics. With 12 years of experience in sales within the electronic wiring harness industry, he manages marketing efforts across Europe. An expert in cable assembly, wiring harnesses, and advanced connectivity solutions, Sam simplifies complex technologies, offering clear, actionable advice to help you confidently navigate your electrical projects.
