Why a traction battery fire is a different problem
Thermal runaway is a self sustaining chemical reaction inside the cells. It produces its own oxidiser, which is why smothering does not work, and it produces enormous heat, which propagates to neighbouring cells and restarts the process. A pack that appears out can reignite hours or days later.
The fire service response is normally cooling with very large volumes of water over a long period, or containment and controlled burn. Neither is something a workshop does with the equipment on the wall.
What the blanket is actually for
Three things, all of them about the building rather than the car:
- Stopping spread. A workshop fire that stays one vehicle is an insurance claim. One that reaches the next three cars and the roof is a business ending event.
- Buying time. Time to evacuate, time to move other vehicles, time for the fire service to arrive.
- Reducing smoke and projectiles in the immediate area, which matters for anyone still getting out.
The car is already lost by the time the blanket is out. Deciding that in advance makes the decision faster on the day.
Quarantining a damaged EV
Most workshop EV fire risk is not a car on a ramp. It is a recovered or damaged vehicle sitting in the yard with a compromised pack, hours or days after the impact.
Common practice is a designated quarantine area, well away from the building and other vehicles, for a minimum of 24 to 48 hours, with the vehicle monitored. Check what your insurer requires, because insurers often specify a longer period and a minimum separation distance, and a claim can turn on it.
Signs of a pack at risk include audible hissing or crackling, smoke or vapour, unusual smell, heat from the underside, and visible deformation. Any of those and it does not come inside.
Choosing and maintaining one
Blankets are rated by the size of vehicle they cover and by temperature resistance, and they are heavy enough that deployment is a two person job in practice. Rehearse it. A blanket nobody has ever unfolded is not a control.
Most are rated for a number of deployments and must be inspected after any use. Treat one that has been over a fire as spent unless the manufacturer says otherwise in writing.