CHIRP Maritime has issued guidance to support both operational and command-level decision-making by identifying EV-specific hazards, behaviours and uncertainties. According to CHIRP, Electric Vehicle (EV) fire risk is different, but not inherently higher. However, unfamiliarity with EV fire behaviour can significantly increase the consequences of an incident if these characteristics are not properly understood and anticipated.
EV incidents on RoPax ferries are low-frequency, high-consequence events. While incidents remain rare, limited operational experience and evolving evidence mean that risk understanding will continue to develop as EV carriage increases. A low probability of occurrence does not equate to low impact. Decision-making should therefore focus on consequence management, escalation potential, and time-dependent behaviour, rather than likelihood alone
Thermal runaway and fire behaviour
Thermal runaway is the defining characteristic of lithium-ion EV battery failure. It can escalate rapidly from localised heating to large-scale gas release, sometimes before any visible fire is present. Battery venting may be energetic and directional, producing jet flames or pressure-release events that differ from conventional vehicle fires.
Once thermal runaway begins, it is difficult to arrest and can involve extremely high energy release rates. Temperatures within the battery pack may exceed 1,000°C, even in the absence of sustained external flame. During this process, large volumes of flammable gases may be released.
In enclosed or semi-enclosed Ro-Ro spaces, these gases can accumulate and migrate, potentially forming an ignition-ready vapour cloud and creating the conditions for a Vapour Cloud Explosion (VCE) if ignition occurs. Early indicators of battery failure do not imply that it is safe to approach. Initial response should prioritise assessment, isolation, and preparedness for escalation over immediate close-range intervention.
Causes of EV battery failure
EV battery failure may result from a range of factors, including:
- Manufacturing defects or material failure
- Battery-management-system faults
- Mechanical damage (including damage from prior road accidents)
- Overcharging or over-discharging
- High ambient temperatures
- Internal or external short circuits
- Ageing and end-of-life degradation
In many cases, the initiating cause may not be immediately apparent.
Fire growth and energy release
Fire growth from EV batteries can be rapid and difficult to control once established, with high and sustained heat-release rates.
State of Charge (SoC) significantly influences severity. A higher SoC increases the peak heat-release rate and the overall energy available. Lower SoC reduces ignition likelihood but may still present significant gas-production and explosion hazards and should not be assumed to represent a low-risk condition.
Gas production and vapour hazards
Thermal runaway releases a mixture of flammable, toxic, and irritant gases. These include lighter-than-air gases (including significant quantities of hydrogen) and heavier vapours that spread unpredictably, accumulate at deck level, or migrate into adjacent spaces.
Early signs may include white vapour, often mistaken for steam or smoke. This vapour is flammable and toxic and can present an explosion risk even in the absence of visible flame.
Hazardous atmospheres can develop away from the vehicle and prior to ignition. The absence of flame or smoke does not indicate a safe environment.
Gases include hydrogen, carbon monoxide, hydrogen fluoride, hydrogen cyanide, hydrocarbons, and other toxic compounds including >100 trace organics. Emerging evidence indicates that exposure to these gases can cause serious respiratory and systemic health effects without appropriate protection.
Ventilation considerations
Ventilation strategies effective for ICE-vehicle fires may not behave as expected during EV incidents. Significant gas production can occur before ignition, and mixed-buoyancy gases may disperse in unpredictable ways within ro-ro spaces. Ventilation should therefore be treated as a tactical decision, based on risk assessment rather than automatic application. Decisions should consider gas dispersion, flammability limits, ignition potential, and explosion risk, which may differ depending on whether the vessel is in port or at sea.
Risk controls and prevention
Advance Declaration
The number and type of EVs and hybrid vehicles should be declared prior to loading, with vehicle locations recorded on the loading plan where practicable.
Booking Declaration
Passengers should confirm that vehicles are in good condition and have not been recently damaged, involved in accidents, or subject to known battery faults.
Check-In Verification
Visual checks should be conducted to identify warning indicators, external battery damage, or other signs that may indicate elevated risk prior to embarkation.
Damaged or Faulty EVs
The carriage of damaged or faulty EVs should be subject to specific procedures, including risk assessment and defined control measures. Some operators may choose to refuse carriage in line with company policy.
Detection & Initial Assessment
Early detection saves time – time is the Master’s greatest ally.
- Use continuous monitoring with CCTV, infrared cameras, thermal imaging, and gas detection (including HF sensors)
- If abnormal heat or smoke is detected:
- Alert the bridge immediately. Crew evacuate and monitor area
- Confirm source and extent (isolated or spreading)
- Inform Harbour Master and initiate SITREP 1
Thermal runaway can develop unpredictably and very quickly. Once confirmed, assume escalation until proven otherwise.
Activation Thresholds & Initial Actions
The Master activates the shipboard response as per SMS and emergency plan.
- Trigger: confirmed or suspected EV fire, or rapid heat rise
- Sound alarm and muster crew
- Consider ventilation control depending on port/sea conditions
- Isolate power and stop vehicle movements
- Begin boundary cooling using fixed systems or monitors Priority: Life before ship, but evacuation timing must balance heat/smoke/explosion risk.
- Situational Awareness & Decision Making
- Maintain shared understanding through:
- Observation (deck condition, smoke, thermal readings)
- Orientation (fire plans and zones)
- Decision (Go / No-Go / Abort)
- Action (implement and communicate immediately)
All updates logged with time and rationale.
Command, Control, and Coordination
- Ship crew: firefighting systems, boundary cooling, evacuation control
- Port/Harbour authority: command, safe anchorage, pollution control
- Fire & Rescue: firefighting and hazmat response
- OEMs/Salvage: technical battery advice
- Regulators: oversight and coordination
- Unified Command: regular SITREPs between all parties
Tactical Onboard Response
- Evacuate non-essential personnel from affected decks
- Continuous cooling with SCBA rotation
- Monitor deck and boundary temperatures
- Maintain clear, short communications
If containment fails prepare evacuation or abandonment to safe anchorage.
Passenger Management
- Simple multilingual instructions
- Muster upwind of smoke
- Prepare for evacuation or shelter-in-place scenarios
- Pre-travel EV safety briefings required
- Port & Harbour Coordination Before arrival:
- Confirm safe anchorage and tug readiness
- Establish exclusion zones
- Coordinate environmental/health response Ports should maintain:
- Stand-off positions
- Evacuation reception plans
- Firefighting and pollution response capability
Information Management
Critical data includes: EV type, battery kWh, SoC, SoH, condition, and deck location. Segregation of EVs recommended. No charging unless risk-assessed.
Equipment & Monitoring
- Thermal, CCTV, gas detection systems
- Fixed deluge and portable cooling
- Contaminated runoff containment
- Drones for observation where authorised
Training, Drills & Learning
- Annual tabletop and live drills
- Multi-agency exercises
- After-action reviews shared
- Crew awareness of EV fire indicators (popping, hissing, vapour, odours)
Oversight & Assurance
Port State Control and Flag Administration should verify:
- EV manifest and SoC procedures
- Monitoring and containment systems
- Drill records and competency
- PPE and firefighting readiness
Post-Incident & Recovery
- Manage contamination and air quality
- Conduct structured debriefs
- Update risk assessments and training
Further essential reading…
The Maritime Professional Council of the UK has produced an essential 48 page guide entitled ‘Lithium-ion battery fires: What we know so far’. The guide is available for free download in PDF format at https://bit.ly/4v1HNF0.