BY DAVID DALRYMPLE
Although we usually deal with gasoline- and diesel-powered vehicles at our motor vehicle responses, electric and gasoline/electric hybrid vehicles are now an everyday reality. However, we must prepare for an ever-increasing array of alternative fuel-powered vehicles in the future. Below is some introductory background information on alternative vehicle power systems and fuels and how they may affect extrication operational guidelines and training.
SHUT DOWN THE POWER
Although each vehicle has unique emergency procedures, before performing any rescue extrication operations you must first shut down the vehicle’s power. With any vehicle, regardless of its power source, perform the following two actions to disable the high-voltage (HV) circuit (found in all electric and hybrid drive vehicles) and to disarm/discharge the supplemental restraint system (SRS) that deploys the air bags:
- Turn the ignition key to the OFF position, remove it from the ignition, and place it FAR AWAY from the vehicle (e.g., on the apparatus) so power isn’t inadvertently turned on. Proximity ignition systems do not use an ordinary metal key; they use a wireless system. In some systems, the key itself need not be inserted into the dashboard or column to start the vehicle; it just has to be within the confines of the vehicle itself.
- Disconnect the 12-volt battery, both positive (+) and negative (-) cables. Note that in more than 40 percent of today’s vehicles, the primary battery is located outside the engine compartment, and some vehicles may have more than one battery. See “Isolate the Power,” Extrication Tactics, Fire Engineering, June 2008, 32-36.
NATURAL GAS
Compressed natural gas (CNG)- or liquefied natural gas (LNG)-fueled vehicles, generally used in public and commercial fleet service, may include cars, trucks, SUVs, and buses. Natural gas’s physical properties make it safer to use than most other fuels. It is nontoxic and has a limited flammability range, approximately between five and 15 percent, and has an ignition temperature of approximately 1,100°Factually greater than those of gasoline and diesel fuel. The fuel density is lighter than air, so with any leak the gas will rise and disperse into the air.
CNG is often confused with LNG. CNG is stored in a gaseous state at high pressure (approximately 3,600 psi), whereas LNG is stored onboard as a purified and condensed liquid by cooling it to 260°F. LNG must be stored in a double-walled, vacuum-insulated pressure vessel and is usually found only in heavy-duty vehicles (photos 1, 2).
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Because of the high pressure involved, CNG vehicles have extremely rugged fuel tanks and fuel systems. Another CNG fuel system safety feature is an automatic release valve that activates in the case of an excessive heat or pressure buildup. The biggest drawback of this fuel is the greater amount of space the fuel storage requires, especially in gasoline-powered vehicles converted to CNG as well as in dual-fuel vehicles that use both gasoline and CNG.
Most CNG vehicles that display a blue diamond label on the passenger side rear are actually CNG conversions of vehicles originally manufactured as conventional gasoline-powered vehicles and may be of any vehicle type or manufacturer (photo 3). The Honda Civic GX, however, is one vehicle sold in the United States that is originally manufactured as a CNG vehicle (photo 4). Although most CNG-equipped vehicles are in fleet service, the number of such vehicles in personal use is increasing now that you can install a natural gas refueling station in your home if it is equipped with natural gas (photo 5). The refueling infrastructure in your state is the greatest limitation. California has the most public CNG refueling stations, with 186 stations of a total of 785 nationwide.
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Dual-fueled vehicles that offer gasoline and either CNG or LPG fuel are common in Europe but are rarely seen here. The driver can switch from one fuel to the other with a flick of a switch.
Responder concerns for these vehicles include proper identification, which is limited to the above-mentioned rear labeling for the most part. Responders can readily detect leaking natural gas because of its distinctive odor; but since gas is lighter than air, it will rise and quickly dissipate. Moreover, in a crash or fire, the fuel system’s automatic shutoff valves close and shut off the flow of fuel to the engine. With CNG/LNG vehicles, the power shutoff/disabling procedures above will also activate the automatic shutoff valves and disable the vehicle’s safety systems. Most of these vehicles also have a manual shutoff valve.
However, if there is a fire, remember that the fuel system will release fuel under pressure when the system reaches a certain temperature. The American Honda Motor Company’s Emergency Response Guide for the Honda Civic GX CNG vehicle advises responders to stay away from the rear of the vehicle until they are certain the fire is out because the pressure relief valve vents toward the driver’s-side rear. Otherwise, responders should use the same precautionary measures used for conventionally powered vehicles involved in a crash for extrication or vehicle fires. Car maker emergency response guides are available at the Moditech Rescue Solutions Web site, www.moditech.com.
PROPANE
The third most popular vehicle fuel after gasoline and diesel, propane or liquefied petroleum gas (LPG) is stored in a tank pressurized to approximately 300 psi, at which point the gas turns into a liquid. However, to use propane as a fuel, it must be converted back into a gas. This is appropriate for applications in which the engine will operate at low speeds with light throttle response, such as forklifts. However, the introduction of liquid injection systems promises to change that.
Many of the same response procedures and concerns involving CNG/LNG vehicles apply equally to LPG-powered units, especially those concerning the automatic and manual shutdown valves and pressure-relief valves. However, identifying an LPG-fueled vehicle varies from vehicle to vehicle, since most are converted from conventional vehicles and are dual-fueled as well.
ETHANOL/METHANOL
Ethanol is ethyl or grain alcohol made from starch- and sugar-based materials such as corn grain or sugar cane or from from cellulosic products such as grass, wood, crop residue, and old newspapers. This cellulosic-based ethanol is much harder to manufacture, since it needs to be broken down into component sugars to be fermented into ethanol. The American LeMans racing series uses this fuel for many of its race cars. In the United States today, 50 percent of the gasoline sold uses a low-level ethanol blend to oxygenate fuel and reduce air pollution. More than a million vehicles in North America can use flex-fuels such as E85 (85 percent ethanol/15 percent gasoline) and E90 (90 percent ethanol/10 percent gasoline).
Methanol, also known as wood alcohol, is made from natural gas but can also be produced from carbon-based feedstock such as coal.
Although extrication response to ethanol- or methanol-fueled vehicles is no different from that of gasoline-fueled vehicles, the firefighting concerns are much different.
Ethanol and methanol fuels have a lower flashpoint than gasoline or diesel. At a fire involving these fuels, the firefighting foams used must be alcohol-friendly, since the fuel’s alcohol content will negate the foam’s properties. Also, fires involving ethanol or methanol blends require a larger foam and water application than those involving straight gasoline or diesel. Although the ethanol fuel used in racing applications will burn colorlessly, E85 and other blended fuels will produce less smoke and soot but will have a visible flame. The Ethanol Emergency Response Coalition (Web site: www.ethanolresponse.com) offers information on E85 and other blended fuels and instructions on how to mitigate incidents involving them.
Labeling for vehicles using such blended fuels is limited, even more so than that of gasoline/electric hybrid vehicles. General Motors products are more prominently labeled than others with a “Flex-Fuel” badging usually found on the rear of the vehicle (photo 6).
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CLEAN DIESEL/BIODIESEL
Today’s petroleum-based diesel fuel is available with ultra-low sulfur content, achieved by blending it with biodiesel. Biodiesel fuels may be produced from biomass, coal, natural gas, or hydrogenation. Although these newer diesel fuels burn more cleanly, are more environmentally friendly, and take a variety of forms in today’s vehicles, responders’ hazards and concerns are similar to those for conventional diesel.
PLUG-IN ELECTRIC/ELECTRIC HYBRID VEHICLES
An electric vehicle gets its power from an electric motor driven by an onboard storage battery. This battery is charged by plugging it into an electric outlet or by a fuel cell that converts chemical energy from hydrogen into electricity. The current limitation on electric vehicles is the battery’s size and storage capacity, which limits its driving range per charge (photo 7).
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Hybrid electric vehicles combine a conventional internal combustion engine with the electric motor and storage battery, which offers the power and range of a conventional engine and the reduced emissions of an electric vehicle.
A plug-in hybrid electric vehicle works much like its cousin, the hybrid electric, but can be charged by plugging into a standard outlet (110 or 220 volts, depending on the vehicle), and it has a larger storage battery and can operate for longer distances on electric power alone (photos 8, 9).
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Although extrication and firefighting considerations for hybrid vehicles have been addressed to some extent, identifying this type of vehicle is still a significant concern for responders. Even though only a limited number of hybrids are on the road, they will increase and include plug-in hybrids and electric-only vehicles. Although most tool evolutions will not involve high-voltage concerns during extrication evolutions, responders must be vigilant and ensure the vehicle’s power is isolated as much as possible. These vehicles do have fire load issues because they employ various alloys that include magnesium (a combustible metal) in their construction and in the high-voltage battery pack. Moreover, future hybrid vehicles will also use gasoline alternatives such as diesel, flex fuel, and hydrogen.
HYDROGEN
Hydrogen is a colorless, odorless gas (H2) that is rarely found alone in nature but is usually bonded with other elements. Because of its density, the volume of hydrogen needed to provide a vehicle-adequate range requires a very large tank with today’s technology, much larger than the typical car’s trunk. Storage technology improvements under consideration include tanks designed to handle up to 10,000 psi, using cryogenic liquid hydrogen cooled to 423°F in insulated tanks, and even chemically bonding it with another material such as a metal hydride. Hydrogen’s low flashpoint and flammability range are the major hazards.
Most current prototype and early production vehicles, such as the Honda FCX Clarity, use a hydrogen fuel cell hybrid system to produce electricity using hydrogen as fuel diffused in a fuel cell system (photo 10). The fuel cell chemically converts hydrogen into an electric current, which then powers a high-voltage motor to drive the vehicle. As with electric and hybrid electric vehicles, high-voltage power is a concern.
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Response to an incident involving a hydrogen-powered vehicle, whether it’s powered by a fuel cell or liquid hydrogen, involves emerging technology hazards. The BMW Hydrogen 7 uses liquid hydrogen in a conventional engine that also runs on gasoline (photo 11). Using hydrogen as a fuel presents the biggest hazard. In the open, any hydrogen leak will rapidly disperse, since the gas is normally lighter than air. However, this fuel can ignite at both lower and higher levels of concentration. In fact, the Emergency Response Guide for the BMW Hydrogen 7 vehicle instructs responders to set up a positive-pressure ventilation fan to blow across the vehicle diagonally to disperse any leaking hydrogen gas. When hydrogen burns, its flame is nearly invisible in the daylight and produces no soot. Current vehicle applications employ a safety valve system similar to that in CNG/LNG vehicles to vent the system safely if overpressurized.
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Leaks from a liquid hydrogen-fueled vehicle would create vapors and ice and make metals coming in contact with it brittle from the extreme cold. A hydrogen leak is especially a concern if the vehicle is in an enclosed area, which may prevent the gas from dissipating and thus present an explosion hazard.
Most of these vehicles are equipped with hydrogen sensors to identify a potentially hazardous atmosphere inside and outside the vehicle. The BMW Hydrogen 7, however, does present one tool evolution concern. Because it’s a dual-fueled vehicle (gasoline/liquid hydrogen), it has a venting system that runs through both C pillars and out a circular disk forward of the shark fin satellite antenna, much like a whale’s blowhole. The Hydrogen 7’s Emergency Response Guiderecommends cutting a roof flap ahead of the C pillars for roof displacement and advises against total roof removal to avoid crushing the vent tubes in the C pillars (photo 12).
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This article does not address the alternative fuels’ storage and dispensing facilities. This technology is still evolving, and we must keep abreast of this aspect of the new motive power technologies, too. Research and educate yourself to be prepared when this technology takes off.
However, even with this new technology, the basics still apply regarding safety and hazard mitigation, tool evolutions, vehicle construction, and so forth. Always be situationally aware and have a backup plan.
DAVID DALRYMPLE, a 26-year veteran of the emergency services, is a career EMS provider for the RWJUH Emergency Services in New Brunswick, New Jersey, and a volunteer rescue services lieutenant for Clinton (NJ) EMS/Rescue. He is the education chair of the Transportation Emergency Rescue CommitteeUS (TERC), a certified international level extrication assessor, a road traffic accident advisor to IETRI, and a member of the IAFC Specialized Technical Rescue Committee. He is a NJ-certified fire service instructor, an ICET-certified registered international SAVER instructor, the lead instructor for vehicle rescue programs at the Hunterdon County Emergency Services Training Center, and the executive educator for Roadway Rescue LLC. He writes for the Extrication Tactics column in Fire Engineering and is a contributing author for its Firefighter I and II Handbook.
