Burning electric cars are no more dangerous in tunnels than gasoline-powered ones

Icon: enlarge

A lot of soot was produced during the attempt by the Federal Materials Testing Institute

First it pops dry, then a cloud of smoke shoots through the tunnel: Researchers from the Swiss Federal Materials Testing Institute have investigated what happens if the battery of an electric car catches fire in a tunnel or an underground car park in a test tunnel in Hagerbach, Switzerland.

Always stay up to date?

Driving reports, analyzes, current news: you won't miss any articles from the Mobility section of SPIEGEL.

The recordings of the experiment seem threatening, flash flames shoot out of the battery pack and generate a lot of soot. The researchers simulated the fire in a small car with a fully charged, 32 kilowatt-hour battery - albeit on a smaller scale. The battery pack used only held four kilowatt hours of energy.

Heat development not higher than with a burner

The distribution of soot and smoke gases, the pollution of the extinguishing water used and the effects on a ventilation system were examined in three different scenarios. The tests were carried out in 2019, but the results are only now available. In terms of heat generation, a burning electric car is therefore no more dangerous than a combustion engine that catches fire.

Icon: enlarge

The researchers set battery modules like this one on fire in the Hagerbach test tunnel

The concentration of highly corrosive hydrofluoric acid, which is considered an additional hazard in the event of a battery fire, also remained below the critical range. Even with fires in tunnels, electric cars do not seem to pose a greater risk than cars with internal combustion engines, and people directly affected by the fire are therefore no more at risk than a conventional car. the researchers judge.

Modern ventilation can also cope with burning electric cars

According to the study, modern tunnel ventilation can cope not only with gasoline and diesel vehicles that have caught fire, but also with burning electric cars. The substances created in this way do not cause severe corrosion on the ventilation or other components in the tunnel - but after the fire, a few things must be observed.

Because a battery fire is a chemical process that cannot be smothered with extinguishing foam as in a conventional car. It must be interrupted by cooling with a large amount of water. Then the wreck must be kept in a water basin or a special container so that it cannot re-ignite.

According to the study, the water used for this can be a problem. The chemical pollution of the extinguishing water was 70 times higher than the Swiss limit value for industrial waste water, and the cooling water was even 100 times higher. The researchers conclude that it should therefore not enter the sewer system without pre-treatment.

Owners of private garages should not remove fire residue themselves

But not only the water, but also fire residues on floors, ceilings and walls require special handling, because "the soot of such a fire contains large amounts of cobalt oxide, nickel oxide and manganese oxide", warns Lars Mellert from the consulting firm Amstein und Walthert, who is also involved in the project was involved. In particular, owners of private parking garages should not expose themselves to any unnecessary risk here, as the heavy metals contained could trigger strong allergic reactions on unprotected skin. "Don't try to wipe up the soot and dirt yourself," warns Mellert.

However, the measurements were carried out with an exposed battery; in electric cars, the power storage devices are usually permanently installed in the vehicle. One can therefore assume "that the pollutants then do not spread so freely in the environment," says the study. For this, however, another attempt with a dummy body is necessary.

ene