Hazard Alternative fuel vehicles (AFV)
Knowledge and understanding
|Alternative fuel vehicles (AFV)||
Understand all associated hazard knowledge
The term 'alternative fuel vehicles' (AFV) refers to vehicles powered by fuels other than petrol or diesel. The hazards and control measures for incidents involving AFVs should be considered in conjunction with those that apply to other road vehicles. AFVs may be difficult to identify from the exterior.
AFVs can be powered by:
- High voltage fuel cells (batteries)
- Compressed natural gas (CNG)
- Liquid natural gas (LNG)
- Hydrogen fuel cells
Where a vehicle is powered by two or more fuel sources, it is referred to as a hybrid. The term most commonly refers to hybrid electric vehicles, which combine an internal combustion engine and one or more electric motors. However, this term includes other mechanisms to capture and use energy.
AFVs may not show signs that that the engine is running, such as engine noise or exhaust gases, emitting, particularly when idling. They may also be restarted remotely or be engaged by a proximity key. Although these hazards are not unique to AFVs they are more likely to be present than in older vehicles or those powered by petrol or diesel.
AFVs affected by collision, fire or submersion may present hazards including:
- Uncontrolled or unpredictable vehicle movements
- High-voltage systems – the residual charge in these systems may remain for up to ten minutes after isolation
- Fuel cell explosion
- Hazardous materials, including liquid petroleum gas (LPG) and lithium ion cells
- Electrolytes leaking from fuel cells
- Pressurised systems
These hazards may also result from operational activity.
High-voltage fuel cell fires
The high-voltage fuel cells that are found in some AFVs, may present amplified hazards if involved in fire. There is a propensity for the fuel cells to reignite after a fire has been extinguished due to thermal runaway; this is a type of exothermic reaction. Copious volumes of water, or other appropriate firefighting media, may be required to extinguish the fire and sufficiently cool the high-voltage fuel cells.
It may not be advisable to move or transport a vehicle with high-voltage fuel cells that have been involved in fire for a prolonged period. The vehicle may need to be cordoned either at the scene of the incident or if put into storage during this time, in case reignition of the fuel cells occurs.