Rail & Mass Transit Sealing: EN 45545 Fire-Safe Solutions

In rail vehicles, a rubber seal is a fire-safety component. Every elastomer in a passenger environment contributes to how a fire would start, spread and generate smoke and toxic gas — which is why European rail sealing is governed by one of the most rigorous fire-safety standards in any industry: EN 45545. This guide explains what EN 45545 demands of seals, and how compliant sealing is engineered for doors, windows, HVAC and glazing.

Why fire safety dominates rail sealing

A train is a confined space carrying many people, often underground or at speed, where evacuation takes time. In a fire, the materials lining and sealing that space determine how much time passengers have. Rubber is combustible unless specifically formulated not to be, and it can produce dense smoke and toxic gases as it burns. EN 45545 exists to control exactly these hazards, and it applies to the seals around doors, windows, HVAC systems and enclosures just as it applies to seating and panels. For rolling-stock builders and their suppliers, fire compliance is not a feature — it is a condition of entry.

What EN 45545 actually requires

EN 45545 is the European standard series for fire protection on railway vehicles. Part 2 — currently EN 45545-2:2020+A1:2023 — sets the requirements for the fire behaviour of materials and components, classifying performance against requirement sets and hazard levels rather than a single pass or fail.

Hazard levels (HL1 to HL3). HL3 is the most demanding; there is no HL4. Importantly, the hazard level is not a property of the material and is not chosen by the seal supplier. It is derived from the combination of *operation category* — from OC1 for surface running, through to OC4 where side evacuation is not possible, as on underground lines — and *design category*, covering standard, automatic, double-deck and sleeping vehicles, both defined in EN 45545-1. The vehicle builder or operator determines the applicable hazard level; the supplier's role is to provide test evidence at the level specified. In practice the large majority of vehicles fall under HL1 or HL2, so specifying HL3 where it is not required is over-specification rather than prudence.

Requirement sets (R1 to R28 in the 2020 edition). Each product is assigned a requirement set according to where and how it is used in the vehicle. For elastomeric sealing profiles, gaskets and hoses the relevant sets are R22 for interior applications — interior window seals, door joints, panel connections — and R23 for exterior applications. The distinction matters: a claim against R23 requires exterior-condition test data specifically, so the two should never be quoted as an undifferentiated pair. Rubber parts serving other functions fall under other sets, including floor composites and cable sheathing.

Test criteria. Across the standard as a whole, reaction to fire is assessed through flame spread and ignitability, heat release, smoke density and the toxicity of combustion gases — but which of these apply depends on the requirement set. For sealing profiles under R22 and R23, conformity is assessed by three tests: oxygen index to EN ISO 4589-2, smoke density to EN ISO 5659-2, and smoke gas toxicity to EN 17084. The thresholds tighten with hazard level — for example, oxygen index of at least 28% at HL1 and HL2 rising to at least 32% at HL3, and maximum smoke density falling from 600 at HL1 to 300 at HL2 and 150 at HL3.

For a rail seal, meaningful compliance means a compound tested against the relevant requirement set at the specified hazard level. Our Westorail™ EPDM and silicone compounds have been tested to EN 45545-2 and meet requirement sets R22 and R23 at hazard level HL3, in the sections covered by our test reports. Test documentation is available on request.

How compliance is actually demonstrated

For a rolling-stock programme, a fire-safe seal is accepted on documentary evidence, not on a supplier's assurance — and it is worth understanding what that evidence looks like, because the language used in the market is often loose.

There is no EN 45545 certification scheme and no certifying body. Conformity is demonstrated by test reports from a laboratory accredited to EN ISO/IEC 17025, supported by a manufacturer's declaration identifying the requirement set and hazard level achieved and listing the associated reports. Under UNIFE guidance, that declaration can only be issued by the actual manufacturer of the end-use product, and it is valid for five years before it must be revised.

Two further points are worth raising with any supplier, including us:

• Which edition? EN 45545-2:2020 replaced NF X70-100 with EN 17084 as the smoke toxicity method. A report citing NF X70-100 was tested to a superseded edition of the standard.
• Which sections? Oxygen index and smoke density are both sensitive to thickness. A declaration should be supported by certificates valid for the thinnest and thickest sections supplied, so extrapolating a sheet result to a thin extruded sealing lip is not defensible.

Ask for the certificates up front and confirm they cover the actual compound, colour and form being supplied, so there are no surprises at vehicle sign-off.

The compounds that meet the standard

Achieving HL3 performance is a matter of compound formulation, not something that can be added afterward. Fire-safe rail seals are built on specially formulated EPDM and silicone compounds engineered to limit flammability, smoke density and toxicity while retaining the mechanical and weathering performance a rail seal needs. EPDM brings excellent resistance to weather, ozone, UV and water for exterior and glazing seals; silicone adds temperature range for HVAC and demanding thermal duty. Both must carry the test evidence — an uncertified EPDM seal, however capable mechanically, cannot go into a compliant vehicle.

Performance beyond fire

Fire compliance is necessary but not sufficient — a rail seal must also survive the operational environment. That means resistance to UV and ozone over years of outdoor exposure, stable performance across the rail temperature range, tolerance of the constant vibration of a moving vehicle without taking a set, and low compression set so the seal keeps sealing over a long maintenance interval. Durability and vibration tolerance are designed in alongside the fire performance, so the tested compound also delivers the service life the operator expects.

Sealing across the vehicle

EN 45545-compliant sealing appears throughout the vehicle, each application with its own demands: passenger and sliding door seals that must seal reliably through high cycle counts, front windshield and window glazing gaskets that resist vibration and weather, HVAC sealing that supports cooling efficiency, and electrical enclosure gaskets that keep out moisture and dust. Many of these are framed seals, produced by extruding a tested profile and splicing and vulcanising it into seamless rings or frames — where the fire performance of the finished part, including the join, should be covered by the documentation you are given. Reverse-engineering of OEM profiles and custom colours to match coach interiors are common requirements alongside the core fire compliance.

Retrofit, refurbishment and colour matching

Not every rail sealing project is a new build. Refurbishment and retrofit programmes frequently need compliant replacements for seals originally fitted before current fire standards applied, or for profiles whose original supplier is no longer available. Here the ability to reverse-engineer an OEM profile from a sample, reproduce it in a tested fire-safe compound, and splice it into the required framed geometry is invaluable — it brings an ageing fleet up to modern fire performance without redesigning the door or window. Custom colour matching to existing coach interiors lets these replacements blend seamlessly with the refurbished vehicle.

Specifying compliant rail seals

• Confirm the hazard level and requirement set your vehicle requires — R22 for interior sealing, R23 for exterior — and remember these are determined by the vehicle's operation and design categories, not by the seal.
• Specify a compound with test evidence at that level and set, not merely a capable EPDM or silicone.
• Check the edition: reports should be against EN 45545-2:2020+A1:2023, using EN 17084 for smoke toxicity.
• Confirm the test evidence covers the section thicknesses you are buying.
• For framed seals, confirm the documentation covers the finished part including the join.
• Verify the service performance too: UV and ozone resistance, temperature range, vibration tolerance and low compression set.

Rail sealing is where fire science, material engineering and long-life durability meet. A compliant seal is one tested to the right requirement set and hazard level, formulated to survive years of vibration and weather, and documented well enough to pass vehicle approval. Specified that way, the humble rubber seal does its part to keep passengers safe.

Key takeaways

• EN 45545-2:2020+A1:2023 classifies fire performance by hazard level (HL1–HL3) and requirement set (R1–R28).
• R22 is interior sealing, R23 exterior — they require separate test evidence.
• For seals, the tests are oxygen index, smoke density and smoke toxicity. Heat release is not among them.
• Hazard level is set by the vehicle's operation and design categories, not by the material supplier.
• There is no EN 45545 certification scheme — conformity rests on accredited test reports and a manufacturer's declaration.
• Fire performance is formulated into the compound; it cannot be added after the fact.

Specifying seals for rolling stock? Talk to us about EN 45545-2 tested Westorail™ compounds and fire-safe seals for doors, windows, HVAC and glazing — with the test documentation your approval process will require.