Fire on board: prevention and fighting

The lesson in plain words

1. Thermal runaway
   • Lithium-ion batteries power phones, laptops, e-bikes, e-foils, outboards and house banks, the boat’s service batteries.
   • Damage, overcharging, poor chargers, water ingress or a fault can start thermal runaway: a cell heats itself, vents gas and sets off its neighbours.
   • The gas is toxic and flammable and can explode in a closed space.
   • Smothering or CO₂ may suppress flames but cannot reliably cool cells enough to stop thermal runaway.
2. Warning signs
   • Watch for swelling, heat, hissing, popping, a sweet or chemical smell, or white or grey vapour.
   • Vapour can come before any flame.
   • Get everyone away from the vapour first.
   • Isolate charging only at a safe remote point outside the affected space; do not touch the battery or operate nearby plugs or switches.
3. Fighting it
   • For a small device, attempt cooling only with charging power safely isolated and without entering smoke or vapour.
   • Use plenty of water from a distance and keep cooling: re-ignition can last hours. Do not handle the battery.
   • A specialist extinguisher must be rated for the battery’s size and may not prevent re-ignition.
   • For an e-bike, e-foil or house-bank pack, withdraw, close the space only if safe, call for help and prepare to abandon.
4. Prevention
   • Use reputable batteries. Charge portable devices with the maker’s charger on a hard, non-flammable surface while awake and present, never on bunks.
   • Charge large portable batteries ashore where possible; stow them dry and secured away from exits.
   • A battery management system (BMS) monitors cells and can disconnect charging or loads when limits are exceeded; it cannot prevent every failure.
   • Installed banks need correct fuses, lithium-compatible chargers and installation to a marine standard such as ABYC E-13.
5. Other prevention
   • Most boat fires start in the engine, the electrics or the galley.
   • Check fuel and exhaust hoses, keep wiring tidy with correct fuses, never leave a cooker or heater unattended, store oily rags in a closed metal tin and keep smoke and carbon monoxide (CO) alarms working.

Key points

• Thermal runaway: cells heat themselves and vent toxic, flammable gas.
• Small device: isolate charging safely before cooling. Water cools; smothering and CO₂ cannot reliably stop runaway.
• Large packs: do not fight; get clear, call for help, prepare to abandon.
• Charge portable devices on a non-flammable surface, while awake and present, with the right charger.
• Installed lithium needs a BMS, fuses and lithium charging profiles; a BMS cannot prevent every failure.

Check what you have read

True or false?

Practice case & exam keys

Exam keys

1. 1Thermal runaway: self-heating, toxic flammable vapour, re-ignition for hours.
2. 2Small device: isolate charging safely; water cools; specialist units have battery-size limits; never handle a hot battery.
3. 3Large pack: evacuate; isolate charging only remotely outside the affected space if safe; call for help, do not fight it.
4. 4Portable devices: maker’s charger, non-flammable surface, awake and present. Installed banks: BMS, fuses, lithium-compatible chargers and marine installation standards such as ABYC E-13.