AP Sensing explains how fibre optic Linear Heat Detection enables earlier lithium-ion battery fire detection on ships through continuous thermal monitoring
On the open ocean, where a ship’s hull is its entire world, fire is one of the few threats that can escalate faster than a crew can respond. Today, that threat is increasingly linked to lithium ion batteries.
Once specialty cargo, they now move through global supply chains in huge volumes, powering electric vehicles, e-bikes, tools, laptops and portable electronics. The maritime industry understands how lithium ion batteries behave under failure conditions.
The chemistry is well studied and the progression from defect to thermal runaway is familiar. What remains difficult is spotting developing thermal events early enough to act. Conventional systems often react only once smoke or fire is visible.
At sea, earlier automatic detection and precise situational awareness can make a critical difference.
How lithium-ion battery fires begin at sea
A lithium ion battery failure usually begins quietly. A defect, manufacturing flaw or Lithium-Ion Battery Fires “The maritime industry understands how lithium ion batteries behave under failure conditions.” impact can cause a small, localised rise in temperature. Inside a battery pack or sealed container, that heat can build slowly and invisibly.
On ships, where containers are tightly stacked and airflow is limited, early detection is difficult. Monitoring still often relies on inspections and fire watches, but thermal events can develop between checks, especially where visibility is restricted.
This is why maritime fire safety is shifting from reacting to visible fire toward continuous, automated awareness of developing thermal conditions.
How fibre optic Linear Heat Detection works
Fibre optic Linear Heat Detection addresses this challenge by continuously monitoring temperature along the protected area.
AP Sensing uses a passive fibre optic sensor cable routed through the ship or cargo zone, creating a continuous sensing line rather than isolated detection points. Wherever the cable runs, temperature is measured.
The system provides thousands of temperature readings along the cable, creating a real time thermal map that updates every few seconds. If thresholds or abnormal thermal developments are detected, it automatically alarms on the bridge, helping crews assess and respond earlier.
How fibre optic sensing detects heat before fire
At the centre of the system is a controller that sends short laser pulses into an optical fibre. As light travels through the fibre, a tiny portion scatters back from every point along the sensor cable.
Part of these backscattered light changes with temperature, while another part remains stable. By comparing the two, the system calculates temperature at every point along the cable. It also measures how long the light takes to return, allowing localised temperature changes to be precisely located.
This creates a complete, real-time temperature profile across the monitored area, not just a reading at one hotspot. Operators can see where heat is developing, how temperatures change and whether a thermal event is spreading.
For lithium-ion battery cargo, where conditions can escalate rapidly, continuous awareness is critical.
Maritime lithium-ion battery fire detection proven at sea
Technology is already proven in demanding environments.
Fibre optic Linear Heat Detection has long been used as a certified special detector within fire alarm systems. Before lithium-ion batteries became a growing maritime concern, it was deployed across road and rail tunnels, parking garages, large photovoltaic installations and storage facilities.
In these settings, reliability is essential. Detection systems must perform despite contamination, electromagnetic interference, vibration, weather and other harsh influences.
Fibre optic LHD has demonstrated this resilience while helping operators maintain safety and avoid unnecessary interruptions. This history is important because the technology is not new to challenging conditions.
At sea, however, airflow, motion and operational constraints create a distinct detection challenge. To explore this, AP Sensing’s system was evaluated alongside conventional and alternative detection technologies in a major European and insurance research initiative focused on fire safety on RoRo (Roll on, roll off) and container vessels. Testing included laboratory work and long-term onboard trials under real operating conditions.
The findings contributed to the inclusion of fibre optic Linear Heat Detection in the maritime SOLAS Fire Safety Systems (FFS) Code in early 2026, reflecting growing recognition of continuous thermal monitoring in maritime fire protection.
AP Sensing’s solution is also DNV-approved for safety-critical ship environments. The results highlighted the limits of traditional smoke detection on ships. In controlled settings, smoke detectors performed well. At sea, airflow, humidity, salt aerosols and engine related particles could delay detection or increase nuisance alarms.
Fibre optic Linear Heat Detection was unaffected by these challenges. Because it measures temperature directly along the cable, it remained reliable regardless of airflow or airborne contaminants.
The trials also showed that the system can reveal how a thermal event develops. It pinpointed the heat source and helped operators track spread and direction, giving crews precise, real-time information instead of a general alarm.
Why fibre optic heat detection suits maritime fire safety
Beyond detection performance, fibre optic Linear Heat Detectors fit maritime operations. The sensing cable is passive and needs no electrical power along its length, simplifying installation and removing potential ignition sources.
The system also remains active during loading and unloading, when cargo handling introduces added risk.
How early heat detection improves maritime fire response
Detecting heat early is only part of the equation. What matters is how quickly and effectively that information becomes action. In a maritime environment, where response time is critical and access can be limited, crews need to know where something is happening and how it is evolving.
Fibre optic sensing provides this insight in real time. Temperature data is processed in the measuring unit and visualised through a graphical user interface (GUI), giving operators a continuous view of conditions across the vessel.
Alarm strategies can be configured around absolute temperatures or temperature gradients, enabling early warnings of abnormal developments before a localised issue escalates.
Lithium-ion battery fire detection beyond maritime transport
With lithium-ion batteries, the challenge does not begin or end at sea. A battery’s journey spans storage, transport, use and recycling. Across these stages, the pattern remains the same: heat develops before fire.
Fibre optic Linear Heat Detection applies this principle consistently. A continuous sensing cable enables early detection and precise localisation, supporting a unified approach to fire safety beyond maritime transport.
This is especially relevant in battery storage facilities, where large volumes of cells are concentrated in confined spaces and in recycling operations, where damaged or unstable batteries add risk during handling and processing.
Across these environments, the value is consistent: early insight enables faster, better-informed decisions and safer operations.
Meet AP Sensing at SMM Hamburg
At SMM maritime exhibition in Hamburg, September 1-4, discussions around lithium-ion battery safety and early fire detection will continue across the industry.
AP Sensing’s fire detection expert, Felix Heck, will be on site to present how fibre optic Linear Heat Detection and Distributed Fibre Optic Sensing are applied in real maritime environments. He will share how continuous thermal monitoring supports earlier detection and more informed response strategies.