Dieter Brants, Hulpverleningszone Oost
The fire load of electric vehicles with batteries and the heat release rate in fire are similar to that of conventional vehicles with fuel. However, the Flanders fire safety organisation (Hulpverleningszone Oost) is concerned about new risks to fire-fighters: chemical and thermal risks from batteries (in particular hydrogen fluoride) and electrical risks (400 – 600 V). Despite these risks, there are still today no rules on charging stations in garages in Belgium, only “guidelines”.
EV chargers are often installed in car parks not equipped with fire detection. Car parks pose specific dangers to fire-fighters: low ceiling increases smoke and toxic gas, problems for containment of contaminated extinguishing water. Low ceilings can prevent access for towing services, whereas vehicles with damaged batteries must be evacuated because of risk of reignition.
Many questions are today unanswered concerning how to deal with electric vehicle fires: How to mitigate the dangers of toxic smoke from batteries in fires? Are sprinklers effective? To what extent will fire spread from one vehicle to another? How to deal with battery fires in larger vehicles (such as buses) for which immersion in a tank of water to prevent reignition is not possible? How to identify and manage fire risks from lithium ion batteries in other appliances?
Vincente Mans, fire safety expert
Fully electric vehicles (EV) do not have conventional fuel, but batteries contain up to 400 litres (five times more volume than conventional fuel) of organic electrolyte with a comparable flash point. Today’s EV have a similar heat release rate to conventional vehicles, but this will increase as stored power increases to offer higher km ranges.
Data suggests that today 50 – 60% of electric vehicle fires occur in garages. Risks are increasing as garages are equipped with multiple chargers, in time one for each parking space. Current car park fire safety regulations and ventilation are designed to address smoke opacity, but toxicity becomes critical with EVs. In addition to hydrogen fluoride from batteries, an increased use of plastics and reinforced polymers in EVs increases fire load and can release glass or carbon fibres or nano-particles.
High voltages and currents in charging pose fire safety risks, because of possible arcing or overheating, so that fire resistant materials are important for safety, in charging installations, cables, connectors and in the EV itself. Fire safety using PIN flame retardants avoids adding further halogenated toxic and corrosive emissions, in case of fire, given that hydrogen fluoride is already identified as an important danger.
Lars Derek Mellert,
Amstein + Walthert Progress
Large scale fire tests of EV batteries carried out for the Swiss Government, with EMPA (see pinfa Newsletter n°117) are looking at the possible consequences of EV battery fires in enclosed structures, such as tunnels or underground car parks.
The brand of battery is not significant, in that the chemistry is the same. A worst case of simultaneous mechanical damage to all battery cells was simulated using a steel wedge. The batteries were standard EV, new and fully charged. Fire, smoke gases and soot were assessed with and without ventilation or sprinklers.
The toxic fire gases found in conventional vehicle fires were released at similar levels, but additionally: fluoride, cobalt, nickel, manganese and lithium (not significant in conventional vehicle fires). These elements were present as aerosols, posing potential health dangers for fire-fighters.
Furthermore, the substances released in an EV fire imply increased toxicity of fire extinguishing water (fire fighting water and water needed for cooling of damaged batteries should be kept separated, if possible), and so increased decontamination costs.
More positively, the tests concluded that EV battery fires are unlikely to cause more critical damage to buildings or infrastructure than conventional vehicle fires.