Fire suppression systems
Fire suppression systems on railway vehicles automatically discharge extinguishing agents into defined zones, controlling or extinguishing a fire before it can spread to adjacent areas or impair evacuation.
Suppression is the active layer of onboard fire safety and noise control: where material standards buy evacuation time passively, suppression systems intervene directly in the fire zone.
The systems are zoned, automatic and agent-specific — the protected area determines the technology.
Zone logic and agent selection
Zone is the primary design parameter, and three agent types cover the majority of railway applications.
High-pressure water mist is the standard technology for passenger compartments. Water stored in onboard cylinders pressurised with nitrogen is delivered through nozzles that atomise the flow to droplet sizes typically below 200 µm.
The fine mist cools the fire zone and displaces oxygen without requiring pre-evacuation of the space, making it compatible with occupied areas. It requires neither sealed enclosures nor pre-warning times.
Gaseous agents — inert gas blends (IG-541, IG-55) and clean agents such as FK-5-1-12 — protect enclosed technical spaces such as electrical cabinets and driver’s desk compartments, where water contact would damage sensitive electronics. Gaseous systems require the protected space to be sealed during discharge and are governed by EN 15004.
Engine compartments and restricted spaces
Aerosol systems use a condensed aerosol-forming compound that generates a mixture of gas and fine solid particles on activation. Compact and self-contained, they suit engine compartments and traction equipment bays where installation space is restricted — at the cost of a residue that requires post-fire cleaning.
Diesel engine compartments present specific hazards: oil, lubricants and fuel at operating temperature, in a confined space with limited ventilation.
Detection in this zone typically uses linear heat detectors — a continuous sensing element routed through the compartment, responding to temperature above a threshold anywhere along its length. Suppression uses high-pressure water spray or aerosol agents rather than mist, which requires higher flow rates to be effective against pool and spray fires.
Regulatory framework
EN 45545 defines the fire safety objectives and material requirements that frame suppression system design. It mandates no specific suppression technology or system architecture — that is left to the vehicle designer in consultation with the infrastructure operator.
EN 15004 governs gaseous fixed firefighting systems. NFPA 130, the National Fire Protection Association standard for fixed guideway transit systems, is referenced in some international procurement specifications but is not mandatory in the EU.
SIL requirements for suppression control electronics are determined by hazard and risk analysis specific to each vehicle type and operator specification.