1 . There's a loud bang, and then it starts: A battery of an electric car is on fire in the test tunnel. A video of the test impressively shows the energy stored in such batteries: meter-long flames flee in disorder and produce enormous amounts of thick, black smoke. The visibility in the previously brightly lit tunnel section quickly approaches zero. After a few minutes, ashes have spread throughout the room.

"In our experiment we were considering in particular private and public operators of small and large underground or multi-storey car parks," says project leader Lars Derek Mellert,"all these existing underground structures are being used to an increasing extent by electric cars. And the operators ask themselves: “    1    ?"But until now there has been hardly any meaningful technical literature, let alone practical experience for such a case. So Mellert developed three test scenarios（场景）, the results of which were published in a final report in August 2020.

“    2    . Besides, they are possibly fatal regardless of the type of drive or energy storage system." says the final report. The primary objective has to be to get everyone out of the danger zone as quickly as possible. The highly poisonous hydrofluoric（氢氟）acid has often been discussed as a particular danger in burning batteries.    3    . The real problem, however, is the extinguishing and cooling water that is produced when fighting such a fire and storing a burnt-out battery in a water basin. The analyses showed that some chemical substances in the extinguishing water goes beyond the limit values for industrial wastewater by a factor of 70; the cooling water is even up to 100-times above limit values.

    4    Firefighters know that the battery of an electric car is impossible to extinguish and that it can only be cooled with large amounts of water. But this is already known to the specialists and is being practiced.