Industrial Fire Journal - Fire & Rescue - Hemming Group Ltd
Comment:electric and hybrid vehicle extrication
Published:  09 November, 2018

As concerns rise over the fire risks of electric vehicles, David Dalrymple examines the specific hazards for rescuers from alternatively-fuelled vehicles and outlines some basic tactics and strategies to follow when attending an incident involving a hybrid or electric vehicle.

The number of XEVs on our roads is growing every year. XEV is the correct term for a group of vehicles that includes hydrogen-fuel power and other derivatives of alternatively-fuelled vehicles. In this issue, I want to focus specifically on hybrid and electric vehicles and consider the critical on-scene concerns for responders.

Hybrid vehicles have been on the scene since 1998, and electric vehicles since 2009. In that time there has not been a single reported case of a responder injured or killed from a high-voltage shock from either type of vehicle. However, we must not become complacent about the on-scene hazards these vehicles pose.

Vehicle hazards

As with every other modern vehicle, hybrids and electrics have SRS safety systems for occupants. In North America, vehicle manufacturers are required to install six SRS in vehicles – frontal driver and passenger, side impact in each seating position, and a curtain SRS on each side of the vehicle. The average, however, is eight to 10 SRS systems plus seatbelt pre-tensioners in new vehicles. The speed, location, severity, and the number of occupants in any motor vehicle collision will dictate the number of SRS systems deployed. More often than not, rescuers will encounter more undeployed SRS systems than deployed SRS.

While undeployed SRS are a hazard, they are a manageable hazard. The best and most effective way to manage undeployed SRS is power isolation. Following the initial steps of power isolation, power off, and key removal shuts down SRS systems completely electrically. (It should be noted here that some SRS use a stored gas inflation cylinder – usually, curtain SRS – and if that cylinder is cut, this can result in an explosive release of gas.) Some recommend removing fuses or service plus, but since these vary from vehicle to vehicle, the most consistent route to power isolation is: shut the vehicle off; remove the key (remembering that many vehicles have proximity keys which must be removed at least 15 feet from the vehicle, and there may be one than one key in play, especially in a family vehicle); and remove 12v power by double-cutting both battery cables.

Besides SRS systems and power isolation, there are a few other things to take into consideration, depending on the emergency. The main concern for all vehicles after power isolation is construction and materials. The strength and resilience of modern materials, coupled with the engineering and energy-absorbing design, can be frustrating to rescuers and pose a challenge for older hydraulic rescue tools. Hybrids and electric vehicles do contain high-strength alloys and even some composite materials. They also usually contain a sizeable quantity of combustible alloys such as magnesium or mag-aluminium, as these materials are strong but are not conducive to electricity. While a non-issue for extrication, these combustible materials are problematic where there is a risk of fire as they support combustion and rapidly oxidise on contact with water, thus making the fire hotter and more violent.

The fire risks of hybrids and electrics deserve some consideration. From an extrication point of view, I believe these vehicles present no more of a hazard than any other passenger vehicle today. However, they present a significant fire hazard that the fire service has been slow to recognise. The combination of a high percentage of combustible alloys, composite materials like carbon-reinforced plastics and carbon fibre, plus a high-voltage drivetrain battery make these vehicles a greater fire hazard than we have ever faced before. If you add in all the existing fire risks in passenger vehicles – undeployed SRS systems, gas struts, gasoline and engine fluids, and non-structural plastics – you could have a serious problem. To suppress fires in these vehicles in the open you need a lot of water – in excess of 7,500 litres (2,000 US gallons) for one passenger car. And, just imagine this scenario in a garage or parking lot.

Operational tactics

Operationally, we approach hybrids and EVs in the same way as any other vehicle. In general, firefighters recognise it is hybrid or electric by its badging or logos during the hazard survey, which means the mitigation strategy is being formulated regardless of the type of emergency. Remember, these are ‘quiet’ vehicles, so EMS crews need to be vigilant because they might need to perform power isolation. At the very least, chock it and remove the key and shut it off so it doesn’t suddenly move while delivering patient care. This is a wakeup call for many EMS crews who didn’t need to worry about this before. 

On the issue of stabilisation, these vehicles have a very low centre of gravity because of their high-voltage battery pack, and this will be oriented differently to most other passenger vehicles. It takes much more force for one of these cars to roll onto its side or overturn, and if it is in such a position it is likely to be resting directly on the roof, neither nose nor rear down, as a consequence of even weight distribution. There will be more weight on the floor, so the vehicle must be more firmly secured when removing or displacing vehicle structure.

Technology aids are an effective on-site tool these days. These include smartphone or tablets apps or laptop software such as Moditech Crash Recovery Software, NFPA Alternative Vehicle app, and Rescue Sheets. These use a variety of methods to identify and display the hazards drawn onto the glass cutaway and colourised. You can remove parts of the vehicle to see interior areas better or layer certain areas for better clarity. They also include all alternatively-fuelled vehicle shut down procedures – primary, secondary, and tertiary – with support photos as well as a full hazard matrix. This information is essential for the development of the correct material displacement and removal plan, and these are resources that the OIC or anyone else on the scene can keep on their tablet and refer to as necessary.

Alongside vehicle hazards, we need to make patient contact and perform power isolation as discussed above. Then, depending on the severity of the incident, and balance of hazards the rest of the operations will mirror every other motor vehicle crash. A key concern across the board is the increasing use of both high-strength alloys and composite materials in the vehicle construction, which requires a heightened awareness when using rescue tools, especially reciprocating saws. Sawing composite materials produces fine powdery dust that is toxic and carcinogenic. You must wear an N95 mask. Do not use your hood pulled up over your nose and mouth.

There will be concerns that are specific to a vehicle type. For example, Tesla models use the entire floor area as the high-voltage battery pack for the car. Tool evolutions such as a dash lift cause undue damage to the high-voltage battery pack and injure the rescuer. The methodology for space making needs to take account of the construction of today’s vehicles. If you can’t break or cut it, widen the existing space, and if that space isn’t enough to disentangle your patient then widen it some more.

Then there are the fire concerns for hybrids and EVs, which are significant. While vehicle manufacturers say that water is ok to use for suppression, you need vast amounts of water if the fire is in an open space, and even more, if the fire is enclosed. A wetting agent is, therefore, the preferred tactic, so that the fire tetrahedron will be hit on multiple sides at once. Foams can work but may have by-products or after effects that are not desirable.

One thing is certain: you must wear your BA during all stages of a fire involving one of these vehicles.

In summary, while hybrids and EVs are unique in their drivetrain, some of their features are just like every other passenger vehicle on the road today. Power isolation is a critical step that must be performed at every injury-producing motor vehicle crash where occupants are still in the vehicle. This goes for all vehicles. Next up we have concerns with SRS systems, however, these have been with us for many years. Time, energy, and focus can be better applied to securing the vehicle hazards as a whole using some of the items mentioned above. This is where the true safety of crew and patients come in. Plus add into this the education and practical training you perform at your stations, academies and elsewhere. All this together is aimed to do one thing: give that patient a better outcome.

Knowledge is nothing if you keep it to yourself.