Guest essay by Eric Worrall
A few weeks ago I asked a fire fighter friend how they extinguish electric vehicle battery fires.
He said “Oh you mean like a Tesla or something? The answer is you can’t. You cordon off the area, and spray a fine mist of water on the fire to try to keep the temperature down until it finishes burning. Takes a few days until it is safe”.
The problem is, besides being highly flammable, lithium is literally the lightest metal. At atomic number 3, it is the first element in the periodic table which is a solid. The two previous elements, hydrogen and helium, are both gasses.
Lithium is so light, it floats on water (lithium density 0.543, half the density of water). Lithium is entirely happy to blaze away while sitting on the surface of a puddle of water.
So if you try to smother a lithium fire with sand, the sand sinks to the bottom, and the lithium floats on top.
Lithium melts at 180C / 356F, and burns at 2000C / 3632F –
almost more than hot enough to melt steel, more than hot enough to destroy most composites and metals like aluminium.
The fumes from a burning lithium fire are highly toxic, capable of causing death or long term dementia like brain injuries – so you need to keep members of the public at a safe distance. Fire fighters need to wear respirators if they approach the flame.
There are chemical extinguishers, but my fire station friend didn’t seem to think much of them, at least not for large lithium fires.
I guess you might be able to smother a large lithium fire by dropping a Chernobyl style sarcophagus made of steel on top of it, or possibly made of some other material which could handle the heat. Then you could fill the sarcophagus with an inert gas like Argon, or just wait for the oxygen to run out. But equipping fire departments with a sarcophagus device large enough to smother an EV fire, and the equipment required to deploy it, would be an expensive exercise.
What does your fire department do when they have to extinguish a large lithium fire? I’d love to know, so I can tell Australian fire departments. Cordon off the area and spray a mist of water at the fire for a few days would be a serious inconvenience or worse, if the burning vehicle was say blocking an important road junction, on the high street, or in someone’s residential or workplace garage or workshop.
Correction (EW): h/t Gordon A. Dressler – steel melts around 1500C, so a lithium fire burning at 2000C is hot enough to melt steel.