Fire safety in underground car parks: how to stay one step ahead

An explosion of a hybrid car in an underground garage had a sequel two days later. The car burned completely under the debris. We’re using these batteries more and more: how safe is that?

Underground car parks: specific challenges

A fire in an underground car park is not comparable to an ordinary building fire. Limited ventilation, narrow entrances, and the presence of flammable materials (cabling, vehicle interiors, stored goods…) make it extra difficult for emergency services to intervene.

With electric vehicles, there is the added complexity of lithium-ion batteries. A chain reaction in the battery can cause it to become extremely heated, releasing flammable gases. That phenomenon is called thermal runaway. If it occurs, it creates an intense fire sequence with heavy smoke development, possible explosive effects, and a prolonged fire that is very difficult to extinguish. Even after extinguishing, aftercare (such as cooling and disposal of the vehicle) remains necessary to prevent re-ignition.

Where are the main risks?

• Charging infrastructure: a faulty charging station or misuse can lead to overheating and short circuits. Mode 2 charging via an ordinary socket is not recommended, as standard sockets are not designed for long-term high loads.

• Lithium-ion batteries: damage, age, or overloading can lead to thermal runaway resulting in fire and explosion hazard.

• Lack of detection and compartmentalisation: without automatic fire detection, emergency stopping devices, and fire-resistant partitions, a small fire can develop very quickly.

• Insufficient organisation: no emergency and intervention plan, no arrangements with the fire or towing service, and no clear management structure significantly increase the risk.

Why take action now?

With increasing electrification, is underground parking still a good idea? Certainly, provided the fire risks have been thoroughly analysed and addressed. A risk analysis is a necessary first step.

Moreover, new legislation is in the pipeline. That will make risk analysis mandatory, both for new garages and existing ones.

Waiting is of little use. A proactive approach not only prevents material damage but can also save lives.