EN 45545-2: Fire Behavior of Materials, R-Sets & Hazard Levels (HL1-3)
EN 45545-2 establishes the material requirements for railway fire safety, replacing older national standards. This guide explains the “Requirement Set” (R-Set) system for categorizing components (Seats R6, Cables R15, etc.), the impact of Hazard Levels (HL1-HL3), and the critical testing metrics: Heat Release (MARHE), Smoke Density (Ds), and Toxicity (CIT).
EN 45545-2 is the core document of the European railway fire safety series. It specifies the reaction-to-fire performance requirements for materials and components installed on railway vehicles. Simply put, it dictates whether a specific plastic, fabric, or rubber can be used on a train based on its flammability, smoke emission, and toxicity.
The standard replaces older national norms (DIN 5510-2, BS 6853, NF F 16-101) with a unified testing regime centered on the “R-Set” (Requirement Set) system, which links the component type to the vehicle’s Hazard Level (HL).
1. How to Read EN 45545-2: The R-Sets
You cannot simply ask for “Fireproof Material.” The testing requirements change based on the component’s function and location. EN 45545-2 divides components into 26 categories called Requirement Sets (R1 to R26).
Requirement Set
Component Application
Key Test Standards
R1 / R2
Interior Surfaces (Walls, Ceilings, Windows)
ISO 5658-2 (Spread), ISO 5660-1 (Heat), EN ISO 5659-2 (Smoke)
R6
Passenger Seats
EN 16989 (Vandalism + Burning), Annex C (Smoke/Toxicity)
R10
Flooring Materials
EN ISO 9239-1 (Radiant Panel)
R15 / R16
Cables (Interior / Exterior)
EN 60332 (Flame Prop.), EN 61034 (Smoke), EN 60754 (Gas)
R22 / R23
Seals & Small Components
ISO 4589-2 (Oxygen Index), EN ISO 5659-2
2. The “Big Three” Metrics
Passing an EN 45545-2 test requires staying below specific thresholds for three critical physical phenomena:
- MARHE (Maximum Average Rate of Heat Emission): Measured in kW/m² via the Cone Calorimeter (ISO 5660). It predicts if the material will fuel a “Flashover.” For HL3, MARHE must typically be < 60 kW/m².
- Ds(max) (Optical Density of Smoke): Measured via the Smoke Chamber. It ensures that burning materials do not create a smoke screen that blinds passengers finding exits.
- CIT (Conventional Index of Toxicity): A calculated value based on the concentration of 8 lethal gases (like HCN, HF, CO) in the smoke.
3. Impact of Hazard Levels
The strictness of the test depends on the vehicle’s classification (defined in EN 45545-1). A material that passes HL1 (Trams) might fail HL3 (Metro/Sleeper). Engineers must always specify the target HL when sourcing materials.
4. Small Parts & Grouping Rules
Not every single screw needs to be tested. EN 45545-2 defines Grouping Rules for small components (weight < 10g or < 100g). If combustible materials are separated by sufficient distance, or their total mass is insignificant, they may be exempt from full-scale testing under strict calculation rules.
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