The use of electric vehicles on event sites, including bicycles and scooters, is increasing. Their positive environmental impacts are well documented. But there needs to be consideration of the safety implications, including the possibility of batteries catching fire. Richard Bate, VP and member of the Sports Grounds and Events Group at Institution of Occupational Safety and Health (IOSH), explores whether the events industry is fully up to speed with the risks created by alternative fuel sources, especially the risk of fires…

Battery electrical vehicles (BEVs) might not seem more dangerous than internal combustion engine (ICE) alternatives, but the component materials of lithium-ion batteries (LIB) mean the fires are very energetic and traditional firefighting techniques don’t necessarily work.

The estimated failure rate (and risk of combustion) of a battery cell is one in ten million. However, given an average EV contains approximately 7,000 cells, the risk increases significantly. Although it is not clear whether electric vehicles are more likely than ICE vehicles to catch fire, the consequences are potentially more significant.

Whilst it can be disconnected, the component that carries the fire risk in a BEV cannot be removed; the battery cannot be drained of electrolyte. Nor is there a tank of fuel which can be drained. An electric vehicle has chemical components that, in specific circumstances, can initiate and sustain an energetic fire.

Two common firefighting techniques are to let the vehicle burn out or submerse it in water, for which there are practical difficulties.

For a BEV, a strategy may be to back off and leave the fire to the professionals. However, the delay may mean firefighters can’t contain it.

Are hydrogen vehicles an alternative?

Hydrogen must be extracted and compressed in fuel tanks before being combined with oxygen in a fuel cell stack to create electricity to power vehicle motors.

While hydrogen is extremely flammable, it is no more or less dangerous than other flammable fuels. Because it dissipates so rapidly (it’s 14 times lighter than air) it would pose less risk in comparison to other fuel sources in uncontrolled conditions.

As a hydrogen fuel cell (HFC) generator doesn’t contain hydrogen, it is simply electronics with no inherent fire risk. An LIB, whether in use or not, still contains the chemical elements for a thermal runaway – where the cell enters an uncontrollable, self-heating state – with the attendant risks of toxic fumes. The Association of Event Organisers recently posited a strong scientific case to show that HFC technology is widely misunderstood and is safer than its LIB equivalent.

What does this mean for event infrastructure fire safety?

It is the interface with the built environment that should most concern the event industry as this brings a potentially serious fire risk that isn’t well understood into the same space as crowded events.

Industry is responding slowly to this change, especially for firefighting tactics for electric vehicles in the most vulnerable settings. While LIBs in a workplace should be treated as any other fuel source, and risk assessed and managed appropriately, the special nature of that risk must also be recognised.

Alternative fuel technologies will be a significant part of the event landscape in future so it is important in the events industry that we understand the nature of the associated risks and how adoption of new technologies can be safely incorporated into the design of events and event venues.