Lessons Learned from the world’s first known case of using a cutting extinguisher on an EV-fire

Håvard Hauge is an experienced Cobra-operator from Vestfold´s Fire and Rescue Service in Norway. But he wasn’t fully mentally prepared for the request his chief was about to make when they encountered their first fully developed EV-fire last January.

Text & interview by Björn Ulfsson/CTIF

Illustrations by Håvard Hauge

Cover photo  from MSB´s full scale test of using cutting extinguishers on EVs in 2022. 

Håvard Hauge was interviewed in a live March 2023 webinar about EV fires. Watch the webinar here

The call came in late one snowy winter evening in January 2023: Garage fire, partially involved.

Vestfold Interkommunale Brannvesen (Vestfold inter municipal fire departments) is a career fire service association just south of Oslo. It has an agreement to support voluntary part time on-call brigades near their jurisdiction, and was called out as back up with a five man team, one truck and a tanker.

Including driving time, the voluntary brigade and Håvard´s team arrived at the same time, about 20 minutes from when the call came in.

The officers from both brigades decide that the Vestfold team would start on the back side of the building plus one of the short end walls, and the voluntary team would  attack the front of the garage with the doors, plus the other short end wall.

The garage was a freestanding wooden structure with 7 stalls in a row, and was estimated to have been built sometime in the mid 90s.

The building was about 45 % involved when extinguishing efforts were initiated. The three middle stalls were entirely involved, with flames through the roof on the middle stall.

According to their normal routine operational procedures, Håvard´s team started cooling the fire gases in the stalls adjacent to those which were already involved. They shot water mist,  mixed with the additive X-fog, through the walls using the Cobra, in the hopes of stopping further fire spread and keeping the uninvolved parking stalls intact.

After about ten minutes of active fire gas cooling, the Vestfold team were called to assist at the front of the building. The garage ports had by then been removed, and access was now  considerably better from that angle.

The commanding officer then discovers a small burning electric vehicle at the seat of the fire. It was very clear that the fire had started in the vehicle, because flames had burned through the roof just above the EV.

It was also clear that the Lithium-Ion battery pack was at this point fully involved and had been burning for a while.

(Investigations have later showed that the fire in the EV had started as a conventional fire in the engine room due to an electrical problem. The fire did spread to the battery pack but had not started there).

The commanding officer then asked Håvard if he would consider using the Cobra to extinguish the battery pack. This was several weeks before MSB published the results from their fire tests on lithium batteries, and no-one at the Vestfold brigade had heard of this method before.

“My spontaneous answer was; since this had never been done before, we had no procedure or  guidance on how to do it. Therefor, it would have to be on the basis on trial and error”, Håvard says in an interview with CTIF News on May 25th.

After a quick but thorough risk analysis, Håvard decided he felt safe doing the operation based on the following criteria:

• The roof had burnt off, which meant he was clear of confinement in case of a battery explosion, or other unexpected fast propagation in the battery
• The doors had been removed which allowed for a quick retreat
• Everything inside the vehicle had already burnt off, exposing the battery pack
• The lance of his cutting extinguisher is made from plastic, which insulates from electricity
• His feet and the area where he was working were dry  

“I have to admit my pulse was very high when I started preparing to penetrate the battery pack. But it helped that I could see the pack clearly, and didn’t have to go very near the battery. I could also stand with the lance resting on the trunk of the car, which meant I could step back quickly if needed”, says Håvard.

The rear window was already broken, and despite considerable amounts of smoke, Håvard could see three holes, about 8-10 cm (2 - 3 inches), in an adjacent casing angled up 90 degrees from the actual battery pack.

The three holes were situated about where the rear seat back cushions would have been.

Out of the middle hole, jet flames were pulsating, and a hissing sound was heard.

“It sounded like short spurts of a similar high pitch type of sound as a jet engine. ´Pysch…. Pysch´… I have been to many vehicle fires but I have never experienced anything of the this intensity like these jet flames before”, says Håvard.

Every time the hissing sound was heard, a very intense jet flames came gushing out from the middle hole.

Afterwards, Håvard has learned that the three holes are vent holes for the battery pack, and these types of holes are common on EV batteries. At the time however, there was limited visibility and he could only guess that the flames came from the seat of the fire propagation inside the battery.

“I have learned, also after the fact, that it is normal to hear a ´popping´ sound when these vent holes open in order to relieve pressure the battery once they reach a certain temperature”, says Håvard.

The fact that he didn’t hear the popping sound this time tells him the fire had been burning for a considerable time in the battery pack.

“Other than that, it was difficult to know at what stage the battery fire was. Doing the math: it took us 20 minutes to arrive, and then another 30 minutes before I penetrated the battery. It could have easily burned for half an hour, maybe even up to 40-60 minutes before I started cooling it”, Håvard says.

Part of the operational procedure at Vestfold is to always use an IR camera to locate hotspots, in order to know where to apply the gas cooling most effectively.

With the help of the TIC he had located a hot spot just below the vent hole, and decided to not attempt to penetrate the battery case at first, and instead shoot water mist through the vent hole and in towards the cells that way.

“I noticed quite high temperatures inside the batteries, at least 740 degrees C ( 1365 degrees F) under the middle vent hole, “ Håvard says.

Without knowing off by hand the normal burning temperature of lithium-ion batteries, he spontaneously felt these were very unusually high temperatures for a car fire.

Placing the lance in his right hand, and the TIC in his left, he started flooding the battery case with water. He shot full blast, leaning the lance on the trunk of the car, through the broken window and shot straight in, using no abrasive additive.

(In hindsight, Håvard has learned that X-fog should not be used in this type of operation, since the additive contains certain salts which can cause further short cuts the battery and worsen the propagation of the fire.)

Half the temperature inside the battery after 5-6 minutes of cooling

After 5-6 minutes of full blast through the vent hole, Håvard could observe with the TIC that temperatures inside the battery pack were dropping considerably. By the time the temperature had reached 400 C (750 F) he decided to change his tactical approach and wanted to try penetrating the actual battery casing.

He then moved lower and rested the lance on the number of the car. He left about 10 - 15 cm ( 4 - 6 inches) between the nozzle and the body of the car, for safety.

He used water with abrasive agent and shot through the battery casing where the red X is marked on the drawing.

In hindsight, it turned out he had hit the battery pack so perfectly the technicians had assumed Håvard had intimate knowledge of the battery design.

“In reality, it was a shot in the dark, it was sheer luck that I aimed so well. I had no idea,  especially with all that smoke. And my pulse was probably about about 200 BPM when I started penetrating the battery casing”, he says.

At that point, there was a drastic drop in temperature to about 200 C (400 F), and he figured the operation was going quite well at that point.

He then moved to the right rear wheelhouse, with the idea of creating a limit line inside the battery by attempting to stop propagation inside the potentially unaffected parts of the battery.

“However, I don´t know if I achieved a good aim from that angle. It was even more a shot in the dark”, he says.

After analyzing the incident in his head after the fact, Håvard feels that he over complicated the operation, and also pulled back too early.

More holes - more oxygen

Making an extra hole in the battery from the side only meant the introduction of more oxygen to the cells, which meant more of the lithium-ion could continue burning even after cooling.

Lithium-Ion produces its own oxygen during a fire, but it needs a certain amount of innate heat to do so. In order to be fully involved, it also needs oxygen from the air, so Håvard now feels the less holes you make, the better.

“So a better tactic, after initializing cooling through the vent hole, would have been to continue through the trunk for longer, just filling the battery from that one angle. It would have been safer, and more effective. By the wheel house, I was working in an awkward position, with less options for a quick retreat ”, Håvard says.

2-3 hours after extinguishing efforts were ended, some smoke and steam was observed coming gushing out from the the middle vent hole (where the jet flames had been), which told the team that some remaining lithium inside the battery pack had reignited, or at least were smouldering to some degree.

“My main mistake that I can see afterwards, is that I stopped cooling while the temperature was still too high. I shouldn’t have settled for 200 C (400 F). Rather I should have continued until I had reached about 100-150 C,  or even down to 50 C (120 F). If I had done that, I would have removed enough energy from the battery pack that it couldn´t possibly have reignited”, he says.

20 minutes would have been an appropriate cooling time

In total, Håvard used about 15 minutes to cool the battery, 7 minutes through the vent hole, and then about 7-8 minutes through the trunk. (In hindsight, about 20 minutes of cooling would perhaps have been the ideal time. )

He estimates he used about 750 liters (200 US gallons) of water, and he figures with time and practice, an EV battery in an earlier stage of propagation could possibly be extinguished with as little as 250 liters of water. (65 gallons)

20 minutes of cooling = 1200 liters (315 gallons)

“If I compared to the “container tactic” which is an established method in many parts of Norway where a burning EV inside a submerged in water inside a shipping container, this method produces much less contaminated water”, Håvard reflects.

A 20 foot transport container uses 15 - 20,000 litres (4-5,000 gallons) of water which would need to be contaminated before it is discarded. It also requires a crane, and a heavy vehicle to transport the container, with the combined weight of the vehicle and the water.

“We respect the some brigades have chosen that method, but we feel that it is too resource heavy. Also, who pays for the decontamination of the container water? The same goes for filling the container with sand. That’s even more weight, and a lot of decontamination”, Håvard says.

After this incident, Vestfold fire & service have done tests with fire blankets for EV-fires, but found that they also fall short on the decontamination issue.

“We find lithium fire blankets are better used as calling blankets on adjacent vehicles, to stop radiant heat and propagation to spread to uninvolved vehicles”, Håvard says.

Vestfold fire & rescue association has had cutting extinguishers in their stations for over a decade, but it’s only in the last few years that the use of them has really taken hold and become part of the standard operational procedures.

“Now it is so established that you never had to motivate why you used it, but rather why you didn’t use it”, Håvard says.

He emphasized the tool cannot actually put out a fire - just like the water mist function on a variable nozzle is not used to attack the seat of a fire in a building,  a cutting extinguisher is primarily used to cool fire gases (often to prepare for PPV) and thereby create a safer environment before an interior “smoke diving” attack is made.

Choose the correct tool for the situation: Knowledge in fire behaviour is key

“A fire truck is a tool box on wheels, and for us, it is one of many invaluable tools. We don’t say you should always use it; if the room is fully involved, there is no point to use small water droplets, they’ll just evaporate. But we always say ´use your heard, then chose the correct tool´”.

The added value of being able to use a cutting extinguisher also on EV fires has brought an ear perk -  however, EV fires don´t happen often and shouldn’t necessarily be the only reason for a brigade to invest in this type of tool.

“There are several brands of cutting extinguishers established here in Norway, and we encourage the use of them all. But It should be a part of an overall tactic for structure fires, with a thorough understanding of how to use it, with training also in the use of the IR camera, Without strong fire behaviour skills, it wont benefit you much”, Håvard says.

Main learning points:

• Never touch the body of the car, either with your hands, feet or with the lance
• Make sure you have a good retreat route
• Open the doors of the vehicle and use an IR camera to located the hotspot in the floor
• Do not use X-fog om batteries
• Leave 10-15 cm (4-6 inches) between the car body and the nozzle for “insulation” against shocks
• Operate in reasonably dry conditions. Don´t attack the battery if you are standing in pools of water
• When you see good effect and the temperature dropping, continue in the same position until the IR camera shows 150 C (300 F) or less
• Limit the amount of entry holes. More holes means more oxygen to the battery cells
• You don’t need to worry about attacking the hottest part of the battery: all the lithium is likely burned out by the time you reach it. Focus on cooling the parts of the battery which are not yet involved.
• You don’t normally need to take any precautions about “shooting through” the battery case
• One entry hole is usually enough. Once the case is penetrated, the water will break up and reach the cells inside without enough power to go out the other side.