What is the primary purpose of EN 45545-2?

The primary purpose of EN 45545-2 is to specify the fire performance requirements for all materials and components used on railway vehicles. It aims to minimize the probability of a fire starting and to control its spread, as well as the heat, smoke, and toxic gases released, to ensure a high level of passenger and staff safety.

What is the difference between Hazard Levels HL1, HL2, and HL3?

Hazard Levels (HL) dictate the stringency of the fire safety requirements. HL1 is the lowest level for low-risk environments. HL2 is a medium level and the most common requirement for mainline trains. HL3 is the highest and most stringent level, applied to vehicles in high-risk environments like underground metro systems where evacuation is difficult. The requirements for heat release, flame spread, and smoke toxicity become progressively stricter from HL1 to HL3.

Does EN 45545-2 only test for flammability?

No, EN 45545-2 evaluates several critical aspects of a material's fire behavior, not just flammability. The key performance criteria include: Heat Release (how much energy a material contributes to a fire), Flame Spread (how quickly fire moves across a surface), Smoke Density (how much visibility is reduced by smoke), and Smoke Toxicity (the concentration of harmful gases produced).

Is EN 45545-2 mandatory?

Yes, for railway vehicles operating within the European Union, compliance with the EN 45545 series is mandatory under the Technical Specifications for Interoperability (TSI). It is the harmonized standard for fire safety on rolling stock, meaning all new vehicles and major refurbishments must use materials and components that meet its requirements.

EN 45545-2: Europe’s Pillar of Rail Fire Safety Explained

EN 45545-2 sets crucial fire safety standards for railway materials, minimizing risk and enhancing passenger protection through rigorous testing and risk-based hazard levels.

December 15, 2024 2:02 am

Understanding EN 45545-2: Fire Protection on Railway Vehicles

EN 45545-2 is the European standard that specifies the reaction to fire performance requirements for materials and components used on railway vehicles. Its primary goal is to minimize the risk of a fire starting and spreading, and to control the level of heat, smoke, and toxic gases released, thereby enhancing passenger and staff safety in the event of a fire.

This standard is a crucial part of the EN 45545 series, which provides a comprehensive framework for fire protection in railway vehicles across Europe. Part 2 is particularly significant as it dictates the specific test procedures, conditions, and fire safety performance requirements for virtually every material used inside and outside a rail vehicle, from seat cushions and floor coverings to cables and external panels.

Core Concepts of EN 45545-2

The standard’s requirements are not one-size-fits-all. They are tailored based on the risk associated with the vehicle’s operation and design. This is achieved through a classification system based on Operation Categories (OC) and Hazard Levels (HL).

Operation Categories (OC)

The Operation Category is determined by the environment in which the railway vehicle operates, specifically considering the time it would take to evacuate passengers to a safe place. There are four categories:

OC 1: Vehicles for operation on open tracks, where they are not expected to stop in tunnels or on elevated sections. Evacuation can be performed to the side of the vehicle onto a trackside walkway.
OC 2: Vehicles for operation in underground tunnels or on elevated sections with side evacuation available, but with potential delays in reaching a safe area.
OC 3: Vehicles for operation on underground or tunnel networks where they can only run to the next station in case of fire, with no side evacuation possible between stations. This includes many metro systems.
OC 4: Vehicles for operation on multi-level underground systems where passengers may have to evacuate through another part of the vehicle, representing the highest operational risk.

Hazard Levels (HL)

The Hazard Level is the ultimate classification that determines the stringency of the fire performance requirements for materials. It is derived by combining the Operation Category (OC) with the Design Category of the vehicle (e.g., standard vehicles, sleeping cars, double-decker cars). There are three Hazard Levels:

HL 1: The lowest hazard level, typically for vehicles with low passenger loads operating in low-risk environments (e.g., some OC 1 applications).
HL 2: A medium hazard level, representing the most common requirement for mainline and regional trains (e.g., OC 2 and some OC 3 applications).
HL 3: The highest and most stringent hazard level, reserved for vehicles operating in the highest-risk environments where evacuation is difficult, such as underground metro systems or sleepers on long tunnel routes (e.g., OC 3 and OC 4).

For a material to be compliant, it must pass the tests specified for its designated Hazard Level (HL1, HL2, or HL3).

Requirement Sets (R-Numbers)

EN 45545-2 groups products and materials into “Requirement Sets,” identified by an “R” number (e.g., R1, R10, R15). Each set corresponds to a specific application or product type and dictates which fire tests must be performed and what performance limits must be achieved for a given Hazard Level.

Examples of common requirement sets include:

R1: Interior vertical/horizontal surfaces (e.g., side walls, ceilings, window frames).
R10: Seats (including cushions, textiles, and interliners).
R15: Floor coverings.
R22 & R23: Seals and gaskets.
R24: Printed circuit boards (PCBs).

Key Fire Performance Test Methods

To determine compliance, EN 45545-2 references a suite of standardized test methods that measure specific fire behaviors. The three most critical aspects are heat release, flame spread, and the density and toxicity of smoke produced.

Heat Release and Flammability

This measures how much energy a material contributes to a fire once ignited. The primary test method is the Cone Calorimeter (ISO 5660-1). The key performance metric derived from this test is the Maximum Average Rate of Heat Emission (MARHE), measured in kW/m². A lower MARHE value indicates better performance, as the material contributes less fuel to the fire.

Flame Spread

This assesses how quickly flames travel across a material’s surface. The standard typically requires testing according to ISO 5658-2 (Lateral Flame Spread). The critical output is the Critical Heat Flux at Extinguishment (CFE) in kW/m². A higher CFE value is better, as it means more energy is required to sustain flame propagation across the surface.

Smoke Density and Toxicity

For passenger safety during evacuation, controlling smoke is paramount. This is evaluated using two main criteria:

Smoke Density: Measured using the Smoke Density Chamber (ISO 5659-2). The test determines the specific optical density of smoke produced over a certain time (e.g., VOF4). Lower values are desirable as they correspond to better visibility.
Smoke Toxicity: Also measured using gas samples from the ISO 5659-2 test, often analyzed via Fourier Transform Infrared Spectroscopy (FTIR). The standard calculates a Conventional Index of Toxicity (CIT) based on the concentration of specific toxic gases (e.g., CO, HCl, HCN, SO₂). A CIT value below the specified limit for the relevant Hazard Level is required for a material to pass.

Hazard Level Requirements at a Glance

The following table provides a simplified overview of the progression of requirements across the Hazard Levels.

Hazard Level	Description	Typical Application	Requirement Stringency
HL 1	Lowest risk level. Materials must meet basic fire performance criteria.	Trams or trains operating on open-air, dedicated lines with easy evacuation.	Base requirements for flame spread and heat release. Smoke toxicity is often not required.
HL 2	Medium risk level. The most common level for European rail.	Intercity trains, regional trains, and some metro systems operating in tunnels.	Stricter limits for heat release (MARHE), flame spread (CFE), and mandatory requirements for smoke density and toxicity (CIT).
HL 3	Highest risk level, for environments where evacuation is most challenging.	Underground metro systems, sleeper trains, and vehicles operating on extensive tunnel networks.	The most stringent requirements. Materials must demonstrate very low heat release, minimal flame spread, and produce very low levels of smoke and toxic fumes.

Conclusion: A Pillar of Railway Safety

EN 45545-2 is a comprehensive and technically rigorous standard that has successfully harmonized fire safety requirements for railway rolling stock across Europe. By establishing a risk-based approach through its OC and HL classifications, it ensures that the level of fire protection is proportional to the operational risks. For engineers, designers, and material suppliers in the railway sector, a deep understanding of its requirements—from R-sets to specific test metrics like MARHE and CIT—is not just a matter of compliance, but a fundamental contribution to passenger safety.