Guest essay by Eric Worrall
A few weeks ago I asked a firefighter friend how he put out battery fires on electric vehicles.
He said, “Oh, you mean like a Tesla or something? The answer is you can’t. They cordon off the area and spray a fine mist of water on the fire to try to keep the temperature low until the burning stops. It will take a few days to be safe. “
The problem is, lithium is not only highly flammable, it is literally the lightest metal. With the atomic number 3 it is the first element in the periodic table that is a solid. The previous two elements, hydrogen and helium, are both gases.
Lithium is so light that it floats on water (lithium density 0.543, half water density). Lithium is happy when it sits on the surface of a puddle of water.
So if you try to smother a lithium fire with sand, the sand will sink to the bottom and the lithium will float to the top.
Lithium melts at 180 ° C and burns at 2000 ° C – almost hot enough to melt steel, more than hot enough to destroy most composites and metals like aluminum.
The fumes from a burning lithium fire are highly toxic and can cause death or long-term dementia such as brain injury. You must therefore keep the public at a safe distance. Firefighters must wear respirators when approaching the flame.
There are chemical fire extinguishers, but my fire station friend didn’t seem to think about them much, at least not for large lithium fires.
I think you might be able to smother a large lithium fire by dropping a Chernobyl-style sarcophagus made of steel on it, or possibly some other material that can withstand the heat. Then you could fill the sarcophagus with an inert gas like argon or just wait for the oxygen to run out. However, equipping fire departments with a sarcophagus device large enough to stifle an EV fire and the equipment required to operate it would be an expensive exercise.
What does your fire department do when they have to put out a large lithium fire? I would like to know so I can tell the Australian fire services. Roping off the area and spraying a mist of water on the fire for a few days would be a serious inconvenience or worse if the burning vehicle is supposed to be blocking a major intersection, on the main street, or in a home or work garage, or garage workshop.