Electric vehicle fire incidents create conditions that are different from traditional car fires, particularly when batteries enter thermal runaway and produce extreme heat, pressure and hazardous gases.
These behaviours have tested existing containment tools and prompted fire departments to look for equipment designed to address EV fires.
America Fire Blanket is one of the companies responding to that need, and former UL business leader Chris Hasbrook has been advising the team as they refine the design of the TREV system and its hazard-management approach.
FSJA Editor Iain Hoey sat down with Hasbrook to discuss how EV blankets are being engineered for operational use.
Electric vehicle fires usually involve lithium-ion battery systems, which behave very differently from gas powered vehicle fires.
A conventional fire depends on heat, fuel and oxygen, and if you remove one of those elements the fire will usually diminish.
Lithium-ion batteries disrupt that principle because one of the byproducts of their failure is oxygen.
Once the battery reaches a critical point of heat, it produces enough of its own oxygen to sustain a process known as thermal runaway, where it continues to burn regardless of external conditions.
When lithium-ion batteries in EVs burn, they reach extremely high temperatures.
They also release explosive and toxic gases, and the fire becomes highly energised and kinetic, ejecting burning battery fragments and hazardous vapours.
This behaviour is far more violent than a typical petrol or diesel fire and it can escalate very quickly.
Water alone does not resolve the situation. If an EV or energy storage system is still energised, applying water introduces a risk of electrocution.
Chris Hasbrook
Water may briefly reduce some heat or gas, but it does not interrupt the reaction driving thermal runaway and runoff carries heavy metals and contaminants into drainage systems.
All of these characteristics combined make EV fires significantly more complex to manage.
There are two main scenarios where a fire blanket might be applied to a vehicle.
The first is when the vehicle itself is burning and the intention is to slow the development of the fire long enough for first responders to evacuate people or secure nearby property.
The second is when a nearby vehicle is burning and the blanket is used to prevent the fire spreading to an adjacent vehicle.
In either case, trained first responders would ideally cover the entire vehicle to contain heat and shield the surroundings.
Thermal runaway can sustain temperatures approaching 1800 degrees Fahrenheit, so a blanket designed to tackle this must be made of a material that can cope with extreme heat while remaining structurally intact long enough for first responders to perform critical tasks such as evacuation or securing the scene.
Earlier this year, I witnessed a series of large-scale research tests where an electric vehicle was intentionally put into thermal runaway.
Chris Hasbrook
Firefighters applied a standard EV blanket and attempted to contain the fire.
When they lifted part of the blanket to vent the gases, the pressure built up underneath and released violently enough to potentially knock several firefighters backward.
Thankfully no one was injured, but it was a clear demonstration of the danger posed by gas accumulation under a fire blanket.
Allowing those gases to escape and mix with air could help them dissipate and could reduce the potential for an explosion or fire extension.
A venting system in an EV blanket that directs gases away from first responders is an innovative and practical idea.
Being able to manage build-up of smoke and gases under an EV fire blanket safely is an important safety development. Managing gas safely is as important as managing heat.
The challenge is balancing the intense heat of a lithium-ion fire with the rapid production of hazardous gases. If those gases are trapped, the pressure can rise to dangerous levels, as I have seen firsthand.
Managing that build-up without creating another hazard is a significant engineering challenge.
A containment tool has to withstand the heat long enough to be effective while allowing enough controlled venting to prevent an explosive release.
That balance is not easy to achieve.
Standards Development Organizations recognise that related standards must be improved to address realities observed in the field and standards development bodies are engaging with industry participants to work to address emerging risks.
Across the world, fire professionals acknowledge that the state of the art is not yet meeting operational needs and the consistency of these discussions shows how challenging the problems of mitigating and managing EV fires remain.
Full-scale trials involving real vehicles and controlled ignition scenarios tend to be the most informative.
The test I observed earlier this year, where electric vehicles were purposely put into thermal runaway, involved large power sources, EV system overload conditions and live application of blankets by firefighters.
Chris Hasbrook
Seeing how the fire developed, how the gases accumulated and how first responders interacted with the equipment revealed practical issues that smaller-scale tests simply cannot show.
It is these kinds of real-world EV fire trials that expose the fire pressure dynamics, the kinetics of battery failure and the limitations of certain containment methods, giving a real-world opportunity to test how an EV fire solution will perform.
