Update on Lithium-ion fire suppression in small devices

After reading “What is the fastest and safest method for putting out a lithium-ion battery fire?“, frequent correspondent “App” wrote:

According to the FAA, water is not a last resort…it’s your first choice, because you don’t only want to put the fire out, you want to cool it, too. So a water fire extinguisher does both at the same time. If you use anything else, then you need to use water too, to cool the rest of the batteries afterwards, otherwise the rest of your batteries may overheat and also catch fire, multiplying the problem by the total batteries involved. This FAA training video demonstrates various methods for putting the fire out, and some things not to do, such as throwing ice on it. https://www.youtube.com/watch?v=vS6KA_Si-m8

Nice video, App! Thanks!

But I think some of that is situational: On a plane, water (or coffee/juice/soft drinks, etc.) are almost always at hand or close by. Plus, in the confined space of an aircraft at altitude, not releasing a cloud of fire-extinguishing chemicals into the air is probably wise!

But a decent home/office fire extinguisher has vastly more fire-suppression strength than a bottle of water. For example an utterly conventional 3A-40BC home/kitchen extinguisher like this has the same suppression power as almost 7 gallons/25 liters of water — that’s almost 50 bottles worth! — and can control a fire even if it’s spread up to about 40 square feet/3.7 square meters in extent. (Fire extinguisher ratings explained.)

Foam-based extinguishers are even better for LI-ion fires because, like liquid water, foam can suppress a fire by cooling the burning material while also cutting off the fire’s oxygen. I have a lot of LI-ion devices in my office (including large e-bike batteries), so I have a fire extinguisher rated at 8A-70B, meaning it has the suppressive capability of around 18 gallons/68 liters of water; and can handle fires up to 70 square feet/6.5 sq. meters in extent.

It would take something like 136 standard water bottles to provide the same fire-fighting capability. 🙂

So, you’re right — a bottle of water or a cup of coffee can work to put out an incipient Li-ion fire; and in some cases (e.g. trapped in a plane at altitude!), it may be the best available option immediately at hand. If that’s what you have, use it!

But when there’s a better option available — e.g. an appropriately sized and rated fire extinguisher — for sure use that instead!

Thanks for writing, App!

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