In 2023, the International Union of Marine Insurance  published a set of best practice and recommendations for the safe carriage of electric vehicles. This was part of its ongoing support of loss prevention guidance to the global marine insurance and shipping sectors. The association has –  published an updated version titled “Risk mitigation for the safe ocean and short-sea carriage of electric vehicles”.

IUMI Secretary General, Lars Lange, explains:

“The volume of cars being shipped by maritime transport globally is around 20 million units per annum. EVs have been transported in ever larger numbers since 2017. There appears to be an increasing frequency of fires onboard car carriers although none to date have been found to be solely attributable to an electric vehicle – although it is possible that an EV was the culprit. However, we are well aware that the characteristics of an EV fire are different to those emanating from a standard internal combustion engine vehicle (ICEV) and it is important that carriers, operators and insurers understand the risks involved and the measures that might reduce that risk. This is why we published loss prevention and safety guidelines two years ago. However, this sector is rapidly evolving and new research continues to report new findings. In light of that, we have updated our paper with new information and adjusted our recommendations and guidance accordingly.” 

Five key areas of the original paper have been updated:

Potential gas accumulation
During thermal runaway, flammable gases may be released. If these gases accumulate in unventilated spaces, they pose an explosion risk. Research into the composition of gases from EV fires is ongoing. Effective firefighting must address both extinguishing fires and managing potentially explosive gases, integrating firefighting and ventilation without reducing system effectiveness.

Total energy release and peak temperatures
Recent fire tests indicate that total energy released by EVs and ICEVs is similar, though EVs may exhibit higher peak heat release depending on battery type. Some studies show no significant difference in peak temperatures, while others report EV fires can exceed 1,000°C, compared to ~600°C for ICEVs. For underwriters, the focus should be on overall risk, especially if fires are not rapidly contained.

Challenges with PCTC ship design
Current PCTCs have large, undivided horizontal decks, unlike older subdivided designs, allowing fires to spread rapidly and making containment difficult.

“Fixed First” approach for PCTCs
Fixed firefighting systems should be activated promptly and safely, before manual intervention, as accessing burning vehicles is dangerous. Early system activation prevents fires from reaching EV batteries and spreading. Manual firefighting should only supplement the fixed system to save lives.

Limitations of foam-based extinguishing systems
High-expansion foam may suppress ignition and prevent heat transmission but has drawbacks: complex operation requiring electricity, reduced penetration and heat resistance in new eco-friendly foams, and a high threshold for “fixed first” deployment due to risks of unnecessary release.

The key takeaways from the updated paper are:

• The state of charge (SoC) of batteries within EVs being transported by car carriers should be kept as low as practically and technically possible. Currently, no international requirements for SoC in maritime transport have been agreed.
• Currently no extinguishing agent or system can interrupt the chemical chain reaction occurring in a battery in thermal runaway.
• A comprehensive firefighting strategy must not only consider the firefighting itself but also the management of potentially explosive gases that may accumulate during such incidents.
• While there is general agreement that the total energy released by EVs and ICEVs during a fire is broadly comparable, opinions diverge when it comes to peak temperatures.
• A peculiarity of EVs is the risk of re-ignition which is higher for a longer period than for ICEVs. Precautionary measures to avoid re-ignition of the traction battery must therefore be taken for an extended period after a fire has been extinguished.
• A challenge specific to roro and ropax vessels is the cargo they carry. EVs such as cars, buses and excavators are often used vehicles and so may contain hidden damage.
• PCTCs present some inherent safety challenges stemming from their unique design characteristics. A specific fire risk onboard PCTCs arises from their large, undivided horizontal fire zones.
• Markings that include basic information about the drivetrain of the vehicles could be useful, e.g. colour-coded stickers for EVs, ICEVs, or hydrogen-powered cars.
• Early detection and verification/confirmation of a fire is key to enable successful firefighting operations. These two steps should not be considered as separate but as one single step. Time between detection and confirmation/verification must be reduced to the shortest possible period.
• Onboard PCTCs, the fixed firefighting systems should be applied early, correctly and safely. Manual firefighting by the crew should be a last resort.
• Seeking external help from professional marine firefighters or salvors is recommended whenever possible.
• To improve its usefulness, the CO2 firefighting capacity on board PCTCs should be at least doubled.
• Foam based extinguishing systems onboard PCTCs have notable drawbacks.
• An alternative firefighting option for PCTCs would be a total flood high-pressure water mist sprinkler system. It can be activated even with crew present. A major advantage of water-based systems is their cooling effect and the potential for boundary cooling. Current ship design and construction limitations must be resolved before this option can be applied broadly.
• Dedicated training schemes should be developed for seafarers sailing on PCTCs.
• A fundamental obligation for the shipping industry is the proactive exploration of improved onboard firefighting capabilities.

IUMI is a member of the IMO Correspondence Group on this subject which reports to the IMO Sub-Committee on Ship Systems and Equipment (SSE). This group reported to SSE 11 in March and is currently working on an action plan to enhance fire safety measures for ships carrying new energy vehicles.

We are grateful to the members of our Fire Protection Working Group for compiling this paper.