by Thom Zaremba, shareholder at Roetzel & Andress
Today, we examine the question: Do the risks of runaway fires posed by the almost overnight proliferation of lithium-ion battery-powered devices into virtually every occupied space of our built environment warrant a second look at the building code provisions that traded off—i.e., eliminated—fire-rated exit access corridors in favor of requiring sprinklers?
According to the 2024 International Building Code (IBC), an exit access “leads from any occupied portion of a building or structure to an exit.” From there, the exit leads occupants to an exit discharge outside the building.
Whether an occupancy is sprinklered or not, every exit between the exit access and the exit discharge must be constructed of fire-resistant material. But fire-rated protection is usually not required for the exit access areas that lead people to the exit! Sprinklers alone protect them.
How dangerous are lithium-ion fires? To find out, let’s take a closer look at how a typical lithium-ion fire unfolds.
The Thermal Runway
First, the internal temperature of a cell in the battery begins to rise. The accumulating heat begins to break down the battery’s internal materials, releasing heat and flammable gases. That is the start of a chain reaction that begins to involve the other cells of the battery. Increasing heat releases more energy, which, in turn, releases even more heat, which releases more energy. When the reaction becomes self-sustaining, it’s called “thermal runaway.”
What happens next can quickly spread a lithium-ion fire throughout a room. Lithium-ion batteries contain liquids called electrolytes. When they begin to boil, a jet of toxic, flammable gas will shoot into the room. The resulting fire will burn at extraordinarily high temperatures that can exceed 1,800 degrees Fahrenheit. The chemical reactions fueling the fire cannot be put out using traditional fire extinguishers or water from overhead sprinklers.
The extreme temperatures of a lithium-ion fire can catch nearby papers on fire, which self-ignite at about 425 degrees Fahrenheit, while cotton and polyester fabrics in nearby furniture can self-ignite at a mere 350 degrees Fahrenheit. Wood in furniture can self-ignite at 400 degrees Fahrenheit.
If activated quickly enough, overhead sprinklers can control the spread of a lithium-ion fire. However, the temperatures of runaway lithium-ion fires accelerate with blinding speed. Once the chemicals in a lithium-ion battery cell enter the unstoppable state of thermal runaway, its temperature can jump from 212 degrees Fahrenheit to over 1,800 degrees Fahrenheit in a single second—literally, the blink of an eye.
Why Sprinklers Aren’t Enough
While sprinklers act fast, they’re not that fast. It generally takes one to two minutes for a fire to raise a room’s temperature to the 135 to 165 degrees Fahrenheit necessary to activate an overhead sprinkler. Moreover, when overhead sprinklers do activate, the water from them won’t put out runaway lithium-ion fires. While sprinklers are generally considered reliable, data developed by the National Fire Protection Association indicates that, historically, human error, aging components or poor maintenance will result in one in 10 overhead sprinklers failing to operate in response to fires large enough to activate them.
While some technologies capable of stopping chemically fueled runaway lithium-ion fires currently exist and others are being developed, none are readily available. Right now, gas releases from lithium-ion batteries are so toxic and flammable, and the runaway fires that follow the gas releases happen so fast and burn so hot, that any human attempt to contain these fires after they’ve started can be deadly.
The extreme temperatures, speed of ignition and flammable gases fueling an explosive lithium-ion battery fire are so dangerous, I believe that in high-density occupancies, we need to reconsider whether the walls of exit access corridors that separate building occupants from the possibility of lithium-ion fires should be fire-rated—even in sprinklered buildings.
Please join me for my next blog, where I’m planning to pull back the curtain on some more lithium-ion battery secrets!