by Thom Zaremba, shareholder at Roetzel & Andress
In my last blog, we looked at how lithium-ion battery fires unfold. They start with a build-up of heat, followed by internal materials breaking down, the boiling of the electrolytes and, finally, an explosive jet-like release of poisonous and flammable gas. As the chemicals in the battery reach a self-sustaining state of “thermal runaway,” the fire no longer needs any outside oxygen source since the chemical reactions causing the fire create the oxygen needed to fuel it.
These fires are dangerous since the gases they release are not only toxic and flammable, but traditional fire extinguishers won’t put them out. Neither will water. These types of thermal runaway fires don’t go out until the chemicals fueling them are gone.
Prevalence of Lithium-ion Batteries
Despite their danger, lithium-ion batteries are found everywhere. To get an idea of how many, let’s walk into a typical business office with 50 employees on a single floor of a 10-story office building. On average, every employee will have between three and six rechargeable lithium-ion powered devices, including cell phones, portable chargers, laptops, tablets, wireless mice, keyboards, ear buds and headphones. That translates to about 150 to 300 lithium-ion powered devices in active use or being charged in just one of the many offices throughout our building.
Additionally, depending on their capacity, every cell phone battery will have between one and six individual lithium-ion cells, and while every laptop will have a single battery pack, that pack will likely contain between three and nine lithium-ion cells wired together. This means that at any one time, our relatively small office may have as many as 450 to 1,800 individual lithium-ion cells in operation or being charged. The higher the number of cells, the higher the potential fire risk.
With the many lithium-ion batteries already in our built environment and the number growing every day, lithium-ion battery fires are on the rise. Nationally, the number of lithium-ion fires is growing at roughly 10% every year. New York City alone recorded a 70% increase from last year, and Toronto has reported a 36% jump in the number of these fires this year.
Too Hot to Handle
What happens if one of these devices overheats and catches fire? First, someone near it may (or may not) notice it getting warmer, then hot. If that continues, someone may (or may not) notice the device starting to smoke. By then, thermal runaway has started, and the device has become too dangerous to handle or to stop the electrolytes from starting to boil inside and exploding into a jet of hot fire. If the device has more than one lithium-ion cell, each cell will join the first, one after another, like dominoes in a thermal runaway fire.
If the building has an operable sprinkler system, water will eventually cool and slow the spread of the fire. But it will not put the fire out or stop the release of toxic, flammable gases. If for any reason the sprinklers do not operate properly, the fire will quickly spread to the furniture, papers and anything flammable in the room.
The best thing the building occupants can do is immediately exit the building at the first sign that a device with a rechargeable battery has started to give off smoke. My last blog left off asking the question, “Shouldn’t the corridors that separate occupants exiting buildings from thermal runaway fires be fire-rated?”
We’ll have to leave building codes developers to answer that question, but right now, the best thing we can do is tell everyone that rechargeable devices of every kind present a fire danger unlike anything we’ve experienced. We all need to exercise great care when buying them, using them, recharging them and disposing of them.
Overheating may be the only warning you will receive and still have time to react before a lithium-ion powered device begins to smoke, signaling that thermal runaway has begun. Once that happens, the device will quickly explode into jets of flames without further warning, which means you should get as far away from the device as quickly as possible and call for emergency responders.
Stay tuned for my next blog. We’ll look at some of the health hazards associated with just being too close to a lithium-ion battery fire, some standards that govern them and some new ones being developed to address them.