As maritime industries accelerate toward electrification, the U.S. Coast Guard Research and Development Center (RDC) has issued a warning: lithium-ion batteries—the same technology powering the global shift to hybrid and all-electric vessels—pose a unique and evolving threat when things go wrong. The April 2025 white paper, Lithium Battery Fire Hazards in the Maritime Environment, lays out the risks, firefighting challenges, and post-incident dangers associated with lithium battery fires at sea, and offers specific recommendations for vessel operators, responders, and regulators.
The Growing Maritime Battery Landscape
The global fleet of battery-powered vessels has expanded from 142 ships in 2017 to more than 1,000 by 2024, with nearly 1,600 additional vessels on order through 2027, according to classification society data cited by the RDC. Hybrid and all-electric vessels now include ferries, workboats, offshore support vessels, and even deep-draft ships adopting hybrid systems for peak-shaving or auxiliary power.
Meanwhile, ferries and Ro-Ro ships are increasingly transporting electric vehicles and micromobility devices such as e-bikes and scooters—each carrying high-energy lithium batteries that can enter thermal runaway, a self-accelerating chemical chain reaction leading to fire or explosion.
Understanding the Risk
Lithium-ion batteries dominate the maritime electrification landscape, representing roughly 99% of installed energy storage systems. Their appeal lies in exceptional energy density and performance—but that same energy, when uncontrolled, becomes a formidable hazard.
Thermal runaway occurs when internal heat generation exceeds a cell’s ability to cool itself. Once triggered—by overcharging, mechanical damage, or manufacturing flaws—temperatures can soar above 1,800°F (982°C). Electrolyte materials decompose and vent flammable gases that may ignite or explode, especially in confined shipboard compartments. The only proven method to halt the process, the RDC notes, is rapid heat removal or venting to cool cells below the runaway threshold.
Fire Behavior and Gas Generation
Battery fires behave differently from conventional fuel or cargo fires. The RDC notes that lithium-ion fires may feature jet-like flames, flying debris, and sporadic explosions. Decomposing electrolytes can produce flame jets exceeding 2,700°F (1,500°C), with some battery chemistries even generating oxygen that sustains combustion without external air.
Compounding the danger, a large battery system can release enormous volumes of toxic and flammable gas. For a ferry with a 1,050-kWh battery pack, the Coast Guard estimates that complete thermal runaway could generate between 100 and 150 cubic feet of effluent gas—known as thermal runaway effluent gas (TREG). Roughly one-third of that is combustible, including hydrogen, methane, propane, and ethene; the rest comprises toxic gases such as carbon monoxide, carbon dioxide, and hydrogen fluoride. In enclosed spaces, ignition can cause pressures exceeding 100 psi, enough to rupture bulkheads or containment housings.
Invisible Dangers: Toxic and Particulate Hazards
Beyond the flames, the gases and particulates produced in lithium battery fires create serious occupational hazards. The RDC found that toxic gases often make up 60–70% of all emissions, with hydrogen fluoride and carbon monoxide levels exceeding the National Institute for Occupational Safety and Health’s “Immediately Dangerous to Life or Health” thresholds.
Fine and ultrafine particulates—many less than 2.5 microns—carry metals such as nickel, manganese, cobalt, and lithium, as well as organic compounds and fluoride ions. These particles can remain suspended in the air, adhere to equipment, and infiltrate ventilation systems, posing long-term contamination risks for crews, inspectors, and cleanup teams.
Fighting Lithium-Ion Fires
Traditional shipboard firefighting methods offer limited success against lithium-ion blazes. Because the reaction is self-heating and self-sustaining, extinguishing surface flames alone may not prevent re-ignition within the cells.
The Coast Guard’s review found that large quantities of water or low-expansion foam remain the most effective tools—not because they chemically suppress combustion, but because they provide cooling and can interrupt thermal propagation between cells. The National Fire Protection Association recommends a 33% increase in water density for sprinkler systems protecting areas where electric vehicles are stowed.
However, responders must weigh water’s conductivity and its potential to trigger electrocution or secondary short-circuits. Water can also react with lithium salts such as LiPF₆, releasing additional hydrogen fluoride gas.
Alternative agents—such as aqueous vermiculite dispersion and F-500 encapsulator agents—may have niche applications for small-scale incidents or as initial suppression tools, but the RDC cautions that their cooling capacity may be insufficient for large, high-energy marine systems.
Specialized equipment, including high-pressure cutting extinguishers capable of injecting cooling water directly into battery modules, and fire blankets designed to contain jet flames from e-bikes or EVs, can help isolate and delay fire spread—but should not be considered standalone solutions.
After the Fire: Persistent and Hidden Hazards
Even when the flames are out, lithium batteries can remain dangerous. Damaged cells may experience delayed thermal runaway hours or even weeks after a fire. The RDC urges crews to monitor affected batteries for signs such as swelling, hissing, or temperature increases using infrared cameras or thermal probes.
Contamination is another serious concern. Toxic residues and particulates settle on deck surfaces, firefighting gear, and even within runoff water. One study cited by the RDC found formaldehyde levels on firefighter protective clothing exceeded safe skin contact thresholds by more than tenfold after exposure to battery-fire smoke. Metals including cobalt and nickel, as well as organic carbonates from electrolytes, were also detected in firefighting runoff—raising both occupational and environmental safety issues.
Because of these risks, all personal protective equipment (PPE) used in a lithium-battery incident should be treated as hazardous waste, and decontamination protocols—such as carbon-dioxide dry cleaning—are strongly recommended.
The Coast Guard’s Recommendations
Recognizing the widespread adoption of battery technologies aboard vessels and in transported cargo, the RDC offers several clear recommendations:
