EV Fire Suppression: Tactical Blankets vs. Encapsulating Agents

The Water Problem Everyone Talks About

Standard vehicle fires are routine: pull a line, knock it down, overhaul, and pack up. Electric vehicle (EV) fires came with a reputation for the opposite: hotter, longer, impossible to put out, and thirsty. The headlines back that up. Departments have reported using more than 11,000 gallons on a single EV fire in Massachusetts and 45,000 gallons at Nissan's U.S. headquarters in 2023.

Into that gap came products: EV fire blankets and encapsulating agents like F-500, each marketed as the answer. In August 2026 the fire service finally got full-scale, independent data on both, and it changes this comparison.

What the Full-Scale Burns Showed

UL's Fire Safety Research Institute (FSRI) burned 18 vehicles common in North America: 15 EVs and 3 internal combustion vehicles. Nine were free burns; five tested handline suppression with water or water plus F-500; four tested fire blankets, some combined with water. The headline findings:

• EV fires matched ICE fires on fire growth rate, peak fire size, and duration. The passenger compartment's plastics and foams are a major share of the fuel in either vehicle, and with no suppression every vehicle burned out in under 90 minutes.
• You can't cool the pack from outside. Vehicle construction prevented effective cooling of the cells even when crews aimed hose streams at vent holes or damage openings.
• Less water worked better. Knocking down the cabin, then limiting water to exposure protection and keeping the passenger compartment from re-igniting while the battery burned itself out, resolved the incident in under 30 minutes with about 760 gallons. Copious water on the pack was, in FSRI's words, ineffective and unnecessary.

Encapsulator Agents (F-500)

F-500 is introduced through a standard eductor at 3%, and the manufacturer markets it for lithium-ion fires on the basis of encapsulation and improved cooling.

• What the independent test found: FSRI ran F-500 at 3% through the same nozzle and procedure as plain water. The encapsulating agent did not improve fire suppression performance.
• The underlying problem: no agent fixes delivery. If water can't reach cells inside a sealed pack, adding a surfactant to it doesn't get it there.
• The IAFF's position: it has not been presented with any full-scale testing by independent researchers showing that any available product improves the performance of water on battery fires.

Tactical Car Fire Blankets

Blankets work by smothering: they cut oxygen to the flaming fire.

• What they do well: FSRI found blankets can effectively control a passenger cabin fire and can reduce heat and smoke exposure to the surroundings.
• What they don't do: they cannot control the battery fire. Thermal runaway doesn't need outside oxygen, so the cells keep failing and venting flammable gas, including hydrogen, under the blanket.
• The hazard they create: in the FSRI burns, gas accumulated under blankets and released uncontrollably, producing flash fires and deflagrations under the blanket and in confined spaces. Blankets also hid the battery's burning state from the crew. An under-vehicle nozzle used with a blanket added hazards without improving suppression.
• The IAFF's position (June 2025): do not deploy a fire blanket on an EV fire involving the battery, and treat parking garages and other confined spaces as higher risk for flash fires and deflagrations.

Stranded Energy and Reignition

The NTSB studied four EV fires and found that three batteries damaged in high-speed crashes reignited after firefighters had put out the vehicle fire. Its conclusion was that stranded energy in a damaged battery creates both shock and reignition risk that lasts well past the incident, and it found manufacturers' emergency response guides inadequate, calling for vehicle-specific information on fighting battery fires and mitigating reignition. FSRI's recommendation is the same in practice: communicate the reignition risk, escort the tow with a suppression unit, and keep the vehicle quarantined at the tow yard.

Contamination

FSRI measured elevated metals and particulate fluoride from battery fires in smoke, in suppression runoff, and on turnout gear, on top of the VOCs and PAHs every vehicle fire produces. Full structural PPE and SCBA through overhaul, working upwind and uphill, using the reach of the stream, and gross decon on scene apply to every car fire, and more so here.

Tactical Consensus

Water is the default. Hit the passenger compartment with a conventional handline, which also tells you whether the battery is involved. If the pack is off-gassing or flaming and the first knockdown doesn't hold, stop trying to drown it: protect exposures, keep the cabin from re-igniting, and let the battery burn out. Leave the blanket on the rig for battery fires, and spend the F-500 budget on training and decon instead.

Sources

• UL Research Institutes — Full-Scale Electric Vehicle Fire Experiments and Recommendations for Fire Incident Response (2026)
• UL FSRI — Researchers release evidence-based EV battery fire response considerations
• IAFF — Safety Advisory: Use of Fire Blankets on Electric Vehicle Fires (June 2025)
• NTSB — Safety Risks to Emergency Responders from Lithium-Ion Battery Fires in Electric Vehicles (SR-20/01)
• NTSB — Press release on the EV battery fire safety report