Operational Guide · Registers & Logbooks

# Fire Safety of Onboard Battery Rooms (BESS)

A thermal runaway fire in a battery room does not behave like a conventional engine room fire: the new EMSA guidance on Battery Energy Storage Systems exists precisely to close this operational knowledge gap.

BESS battery room thermal runaway hybrid electric

## Operational Explanation

Battery Energy Storage Systems (BESS) installed on hybrid or electrically propelled ships are fixed installations distinct from lithium battery cargo carried as freight: these are large battery banks, often installed in dedicated engine room compartments, presenting a specific fire risk profile linked to the phenomenon of thermal runaway, distinct from a conventional fire.

EMSA has published dedicated guidance on the safety of onboard BESS, recognizing the growing complexity of these installations, with high total energy storage and a risk of fire propagation from one cell to another within the battery bank that requires specific response strategies (massive and prolonged cooling, isolation of the affected bank) distinct from conventional extinguishing techniques applied in the engine room.

## Regulatory Reference

EMSA guidance on the Safety of BESS on board ships: specific recommendations for installation and emergency response in onboard battery rooms. Complementary industry standards such as NFPA 855 (update expected in 2026) and UL 9540/9540A (revised edition 2025) provide technical references on mitigating energy storage system risks, although developed mainly for land-based applications.

## Scope of Application

Every hybrid or electrically propelled ship fitted with onboard battery rooms (BESS), with responsibility on the crew for specific training on responding to a thermal runaway event in these installations.

## Procedure / How to Complete It

1. Identify the location and specific configuration of onboard battery rooms (BESS), distinguishing them from conventional engine room spaces in the emergency response plan.
2. Train the crew on the specific response strategy to thermal runaway in a battery room: massive and prolonged cooling of the affected bank, not conventional extinguishing.
3. Verify the availability and operation of detection and alarm systems specific to the battery room, distinct from those of the main engine room.
4. Consult the EMSA guidance on the safety of onboard BESS to update response procedures specific to the installed plant configuration.
5. Include specific thermal runaway scenarios in the battery room in periodic fire drills, explicitly distinguishing them from conventional engine room fire scenarios.

## Practical Example

Example: during a periodic fire drill on a hybrid ship, the crew simulates a thermal runaway event in the battery room, applying the massive cooling and isolation strategy for the affected bank, distinct from the standard procedure used for a conventional engine room fire, according to the EMSA guidance on BESS.

## Real Cases

Recent studies on lithium-ion battery combustion in engine room fires on hybrid/electric ships have confirmed that the behaviour of the thermal runaway phenomenon, including propagation from one cell to another within the battery bank, requires specifically adapted response strategies, not reducible to the conventional extinguishing techniques already established for traditional engine room fires.

## Common Mistakes Mistake Library

Mistake | Consequence | How to avoid it
--- | --- | ---
Battery room (BESS) treated in the emergency response plan as a generic extension of the engine room | Inadequate response strategy in the event of a thermal runaway event | Treat the battery room as a specific risk area in the emergency response plan, with dedicated procedures
Periodic fire drills that do not include specific thermal runaway scenarios in the battery room | Crew unprepared to apply the massive cooling strategy in a real event | Always include specific thermal runaway scenarios in the battery room in periodic drills
EMSA guidance on BESS not consulted when updating onboard operating procedures | Response procedures not aligned with the most up-to-date industry recommendations | Consult and integrate the EMSA guidance in defining battery room-specific operating procedures

## PSC Observations

PSCOs may verify, for hybrid/electric ships fitted with BESS, the existence of specific emergency response procedures for the battery room and crew training on these procedures, distinct from generic engine room ones.

## Operational Tips

- Don't treat the battery room as a simple extension of the engine room: thermal runaway requires a specific response strategy.
- Consult the EMSA guidance on onboard BESS safety to update operating procedures to your installation's specific configuration.
- Always include thermal runaway scenarios in the battery room in periodic fire drills, distinguishing them from conventional scenarios.

## Checklist

- Location and configuration of the battery room (BESS) identified in the emergency response plan
- Crew trained on the massive cooling strategy specific to thermal runaway
- Detection and alarm systems specific to the battery room verified as functioning
- EMSA guidance on BESS consulted to update operating procedures
- Thermal runaway scenarios in the battery room included in periodic fire drills

## FAQ

What is a BESS on board a ship?
A Battery Energy Storage System: a fixed energy storage installation fitted on hybrid or electrically propelled ships, distinct from battery cargo carried as freight.
Why does a thermal runaway fire in a battery room require a different response from a conventional fire?
Because the reaction self-sustains internally within the cell and can propagate from one cell to another within the battery bank; the correct response is massive and prolonged cooling with isolation of the affected bank, not conventional extinguishing.
Is there dedicated guidance on onboard BESS safety?
Yes, EMSA has published specific guidance on the safety of Battery Energy Storage Systems installed on board ships.
🎬 Additional photos, videos and interactive diagrams for this topic will be available in a future version of the platform.

## Related Topics

Lithium Batteries: Thermal Runaway and Fire Response on Board Blackout and Failure Management

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