Fire suppression systems
Fire suppression systems on railway vehicles automatically discharge extinguishing agents into defined zones to control or extinguish a fire before it can spread to adjacent areas or impair evacuation.
The primary design parameter for railway fire suppression is zone: the protected area determines which agent is appropriate. Three agent types cover the majority of railway applications.
Zone logic and agent selection
High-pressure water mist is the standard technology for passenger compartments. Water is stored in onboard cylinders pressurised with nitrogen and 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 does not require sealed enclosures or pre-warning times.
Gaseous extinguishing agents — including inert gas blends (IG-541, IG-55) and clean agents such as FK-5-1-12 — are used in 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.
Aerosol systems use a condensed aerosol-forming compound that generates a mixture of gas and fine solid particles on activation. They are compact and self-contained, and are used in engine compartments and traction equipment bays where installation space is restricted. They leave a residue that requires post-fire cleaning.
Engine compartment protection
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 that responds 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 the suppression system design. It does not mandate specific suppression technology or system architecture; this is left to the vehicle designer in consultation with the infrastructure operator.
EN 15004 governs gaseous fixed firefighting systems. NFPA 130 (National Fire Protection Association standard for fixed guideway transit systems), referenced in some international procurement specifications, 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.