Hybrid Vehicles: Separating Fact from Fiction


Although they’ve been available for several years, hybrid vehicles are becoming more popular in no small part because of the volatility of gasoline prices. Many myths and misunderstandings concerning the dangers of these vehicles’ new technology have circulated among emergency responders. Separating fact from fiction is paramount to enable emergency responders to properly handle these vehicles at incidents.

Some current myths about hybrid vehicles include the following:

  • Hybrid vehicles are just a fad.
  • A damaged hybrid battery module will leak a significant amount of fluid.
  • Touching a hybrid that has been in an accident or is submerged will result in an electric shock.
  • The high-voltage power system is difficult to disable.
  • The high-voltage wiring hampers vehicle extrications.
  • Hybrid vehicle fires require special equipment.

Clearly, hybrid vehicles and other alternative fuel technologies are here to stay. With the uncertainty of gasoline prices, consumers have turned to hybrids to save at the pump. Recent articles have labeled hybrids as “recessionproof” as the percentage of sales of some hybrid models have continued to increase despite declining sales of other vehicles. Toyota recently celebrated a milestone by selling its one millionth hybrid, and a recent IBM Institute for Business Value white paper estimates that hybrid sales could hit two million a year by 2013.

Although hybrids do present certain new risks to emergency responders, proper education and training can minimize these concerns. For fire departments with proper standard operating procedures (SOPs) for handling motor vehicle accidents (MVAs) involving conventional cars, many of these procedures will remain the same for hybrid vehicles. However, departments should update current SOPs to address concerns regarding hybrids and other types of alternative fuel vehicles. This article presents just a broad overview of the current major hybrid systems available and their function and does not delve into the intricacies of each individual model’s operating parameters. It is just a general representation of the hybrids on the road today.


The hybrid vehicle concept is simple: a vehicle that uses two methods of propulsion that work in conjunction with each other to improve fuel efficiency. Hybrid propulsion is nothing new. In diesel-electric locomotives, diesel fuel powers electric generators that produce electric current to power the traction motors that actually drive the locomotive’s wheels. Old diesel submarines used a similar type of hybrid propulsion. Current hybrid vehicles employ an internal combustion engine and electric motors. Future hybrids that use a hydrogen fuel cell to replace the gasoline engine are being tested.

There are three types of hybrids available on the market today: full, mild, and start/stop hybrids. Although mild is sometimes used to describe a start/stop hybrid, this article will use the terms as defined below.

Full hybrid. Toyota, Lexus, Mercury, Mazda, Ford, Nissan, and some General Motors (GM) models currently use the full hybrid technology. A full hybrid can move at low speeds (approximately 20 mph) using only its electric motors and at higher speeds using both the electric motors and gasoline engine. Advances in technology have increased the speeds at which newer models can reach using the electric motor. The 2010 Ford Fusion hybrid can reach 47 mph on the electric motor alone. Full hybrids are the most fuel-efficient models.

Mild hybrid. Honda uses a mild hybrid system, in which the electric motor assists the gasoline engine during acceleration and operates in tandem with it. In some instances, the electric motor can propel the vehicle by itself.

Start/stop hybrid. This system uses an electric motor to start a vehicle’s engine instantly when it is shut down. Although not considered a true hybrid system by many, since the electric motor doesn’t really propel the vehicle, this system does increase gas mileage by reducing the amount of time a vehicle’s gasoline engine runs when it is not necessary. The vehicle’s engine is automatically shut down when it is coasting and traveling under 15 mph, braking, in Drive with the vehicle stopped, and in Park. A large electric motor replaces the traditional starter and alternator system and instantaneously starts the engine when necessary and charges the batteries. Provided that the ignition is on, the engine starts when the driver releases his foot from the brake or when engine power is required. Although initial research indicated that this hybrid type would most likely be slowly phased out in the future, Toyota is discussing plans to release its own start/stop hybrid.

Many car manufacturers have invested significantly in developing their hybrid system battery designs. Tables 1 and 2 list the hybrid models that are currently available, discontinued, and expected to be introduced in the future.




Only two hybrid models, the Honda Insight (discontinued in 2006, rereleased in the 2010 model year) and the Toyota Prius were designed specifically as hybrids. Other hybrids are adapted from preexisting conventional model chassis. Be aware that even an ordinary, familiar-looking vehicle could be a hybrid. Simply looking for a “space-age” style car is not sufficient.

You can identify a hybrid through formal and informal methods. Formal methods include searching for vehicle badges or logos that formally spell out “hybrid” or the particular manufacturer’s terminology for it. Informal identification involves looking for the visible changes made to the vehicle to transform it into a hybrid.

Formal. Although hybrid symbols are the easiest and potentially the most obvious method of identification, do not rely solely on this type of identification. The absence of a visible indicator does not immediately mean you are not dealing with a hybrid. Depending on how well the vehicle is marked and the extent of the collision, these logos can easily be damaged or hidden. Some models, such as the Lexus RX400h, may not use what would be considered a traditional hybrid emblem. In some model years, only the “h” in the RX400h badge signifies the vehicle is a hybrid.

Hybrid logos are most commonly found on the rear of the vehicle, the front or rear doors, or the front fenders (photo 1). Some models may only have a logo on the rear of the car; consider that these logos could become hidden in a rear-end collision.

1) Photos by author unless otherwise noted.

Additionally, the words “hybrid” or the manufacturer’s hybrid system name (e.g., on Honda hybrids, “Integrated Motor Assist” or “IMA”) can be found on a plastic cowling in the engine compartment and on the vehicle’s dashboard instrument panel.

Informal. When you know what to look for, you may find informal identification just as effective. The most notable informal hybrid identifiers are the orange cables for the high-voltage electrical lines and the blue or yellow cables (depending on manufacturer) to indicate medium voltage. These cables can be found in the engine compartment, on the underside of the vehicle, and in the area where the high-voltage battery is stored.

Be careful, however, since manufacturers have begun to conceal the majority of the cable on the underside of the vehicle in a black cladding, leaving very little exposed for emergency responders to see. In several models, such as the Ford Escape, Mercury Mariner, Mazda Tribute, and Toyota Highlander (photo 2), only a few inches of the orange high-voltage lines are visible. Some models, such as the Nissan Altima hybrid, do not have any visible orange wiring, since it is completely encased in a black plastic protector.


Car manufacturers have also placed high-voltage warning symbols in the areas where the orange cables are present. You may also encounter a yellow medium-voltage cable (34 to 42 volts DC) used for power steering. Blue medium-voltage cables are used in several GM models such as the Chevy Malibu hybrid (photo 3).


Other informal hybrid identifiers are battery vents in various locations throughout the vehicle. The high-voltage battery’s constant charging and discharging produces heat that needs to be dissipated. Not all models will have visible vents, but be on the lookout for the following: In the Ford Escape, Mercury Mariner, and the Mazda Tribute hybrids, vents are on the driver’s side rear quarter glass (photo 4). The early version of the Toyota Prius (first generation) had the vent built into the driver’s side C post. The Toyota Highlander and Lexus RX400h have vents under the rear passenger seat (photo 5). In several of the sedans, the battery vents can be found on the rear deck (photo 6). To improve efficiency, these vents are typically located in the general vicinity of the battery pack.






An additional informal identification method includes a battery status indicator found on the dash. This is usually a digital or analog gauge that indicates whether the batteries are being charged or if they are being used to assist the vehicle’s propulsion. You may also encounter a kilowatt gauge, which has replaced the tachometer in some models.

Finally, all but a couple of models have incorporated some type of a “Ready” indicator into the dash display that responders can use to determine if the vehicle is truly off or simply in its “Ready” mode and will move as soon as it is placed in gear or the driver’s foot is removed from the brake. This issue is explored in greater detail later in this article. This “Ready” indicator can range from an actual “Ready” light to an “Auto Stop” indicator (photo 7). The Emergency Response Guides (ERGs) available from the manufacturer illustrate the specific indicator in each model.




Depending on the hybrid’s make and model, you may encounter high- and medium-voltage systems. Most models on the road use a high-voltage electrical system, which is used on the full hybrids as well as the Honda mild hybrid system. Some of these high-voltage models use stepped-down medium voltage for the electric power steering system; this wiring is typically yellow. Most start/stop hybrids use blue wiring to indicate medium-voltage electrical lines (GM models).

The hybrid system’s three major components include the electric motor/generator, the high-voltage wiring, and the high- or medium-voltage battery. The electric motor assists in propelling the vehicle and recharges the battery.

Two methods are used to recharge the battery. In the first method, the gasoline engine turns the electric motor/generator to produce electricity. In the second, regenerative braking, the electric motor assists the brakes in slowing the vehicle. In this process, the electric motor reduces the vehicle’s kinetic energy and turns it into electricity instead of wasting it as heat when the brakes are applied. The motor’s turning produces electricity to recharge the battery and reduces the vehicle’s speed at the same time. Orange high-voltage cables that conduct electricity from the motor to the battery and back again are found in the engine compartment, on the underside of the vehicle, and in the battery compartment.

The high-voltage nickel-metal hydride (NiMH) battery modules capacities can range from 144 to 330 volts DC. The basic battery concept is consistent, although some modules differ in layout slightly. One design uses several low-voltage cells (each cell about the size of a D battery) arranged into a “stick”; several sticks are combined to create the module. The Toyota Prius as well as many other hybrid modules use a battery stack consisting of prismatic NiMH cells connected in series (38 in the Prius). These are a series of flat battery cells sandwiched together.

This NiMH battery stack is considered a dry cell and does not present a significant hazmat spill hazard. The cell’s plates absorb the potassium and sodium hydroxide electrolyte, forming a gel that will not normally leak, even if the battery is damaged in a collision. If the battery is crushed, however, it is possible for a small amount of electrolyte to leak. In the very rare instance that this would occur, vinegar would neutralize the electrolyte. The industry is currently looking at using lithium ion and other battery and capacitor technologies to improve efficiency.

High-voltage batteries are typically located behind the rear seat in sedans and are either under the rear seat or the cargo area in SUV models. All hybrids use a standard 12-volt battery system to power standard low-voltage systems. In some hybrid models, such as the Toyota Prius and Camry, the Nissan Altima, and the Lexus 450h, the 12-volt battery is in the trunk.

Start/stop hybrids typically use medium-voltage systems with voltages ranging from 36 to 42 volts. Battery locations are typically the same as those in high-voltage applications, although the batteries are smaller and hold less voltage. Most of these batteries are NiMH as well, although some models, such as the first-generation GMC Sierra and Chevy Silverado hybrids, use an electrolyte starved-lead acid battery. Medium-voltage wiring can also be found in the same areas as high-voltage wiring, although the coloring is usually different. GM manufactures most of the start/stop hybrids on the market today; in most GM models, blue wiring indicates intermediate voltage.


Numerous safety features are built into hybrid vehicles to prevent occupant and emergency responder injury. Additionally, the positive and negative cables are completely isolated from the chassis to prevent any electric shock hazard resulting from touching the chassis itself. Any type of short circuit in the system resulting from the cable contacting the chassis or another object will activate the high-voltage fuse. Numerous other diagnostic controls ensure that the high-voltage system functions properly and will shut it down should any abnormalities arise. Keep in mind, however, that although these safeties will disengage power to the high-voltage system, the battery will still remain energized.

In the full hybrid systems, normally open relays (powered by the 12-volt battery system) control the power flow from the battery through the high-voltage system. Hybrids employ safety switches designed to automatically open these relays in a collision severe enough to activate the vehicle’s occupant protection systems (i.e., air bags and seat belt pretensioners). This prevents high-voltage power from flowing out of the battery. The relays are also opened when the ignition is turned off, the battery is disconnected, or the high-voltage system fuse that powers the relay is removed; all of these actions remove the 12-volt power from the relay, returning it to its open position.

Honda’s mild hybrid systems operate slightly differently. Since this system operates under different parameters than a full hybrid, the high-voltage power flows through the system only during acceleration; deceleration; and, in some models, when the vehicle’s air conditioning is running. As with full hybrids, the high-voltage system is disengaged when the ignition is turned off, the battery is disconnected, or the fuse controlling the system is removed. Additional safety features for individual models can be found in the ERGs.


High-voltage electricity and unexpected vehicle movement are the two dangers emergency responders should be most concerned with. Although death or serious injury can result from coming in contact with high-voltage electricity, extensive safety systems and strict adherence to proper safety procedures greatly minimize this danger. Although the media and other entities have hyped the dangers of hybrids, proper training and understanding of hybrid technology make them one of the smaller issues with which the fire service must contend. I drive a hybrid and am not concerned that I am placing myself, my family, or my fellow firefighters in unnecessary danger.

High voltage. As previously mentioned, the high-voltage battery modules’ capacities can range from 144 to 330 volts DC. Some models contain a boost converter that transforms the DC power from the battery to 650 volts AC for the electric motors to operate on. Testing indicates that high-voltage systems can remain energized even after fire exposure, primarily because the relays can melt in the “closed” position and allow the high-voltage circuit to stay engaged. Avoid contact with any high-voltage components, and never attempt to disconnect any high-voltage connections. Although they are not technically high voltage, follow the same precautions for yellow or blue medium-voltage cables as well.

Vehicle movement. Statistically speaking, the primary danger to emergency responders is that the vehicle can move instantaneously even though it may appear that the vehicle is off. A primary hybrid vehicle energy-saving feature is its ability to shut down the engine when the vehicle is stopped. This could give a false indication to an emergency responder that the vehicle is off and therefore will not move under its own power. The Honda Insight and hybrid models from Ford, Mercury, Toyota, Lexus, Nissan, and GM incorporate some type of “Ready” light (photo 8) or other indicator on the instrument panel to advise the driver that it is in a “Ready” status and will move if the accelerator is depressed or the driver’s foot is removed from the brake. Establish departmental procedures that prevent this potential movement before placing yourself in the front or rear of the vehicle. Controlling potential vehicle movement should always be a priority, even if the vehicle is a hybrid.




Emergency responses to hybrid vehicles vary only slightly from a standard response. Just adhering to accepted fire service standards and procedures for handling MVAs will address many hybrid vehicle concerns.

Never attempt to disconnect any high-voltage components or touch damaged/broken orange cables or a damaged battery. Always treat high-voltage cables as if they were energized. Although there are no extrication techniques specific to hybrids, when cutting, always consider the location of high-voltage wiring. Manufacturers have placed high-voltage wiring and batteries in areas that are not typically considered cut points. However, if the vehicle has suffered extensive damage, consider that these components may interfere with established cut zones, and plan accordingly.

In some situations, because of the high-voltage battery’s location in the Honda Civic and Accord hybrids, between the rear seat back and the trunk, you cannot use the more advanced technique of trunk tunneling. Based on a quick review of available models, it appears to be a common practice to run the high-voltage cable on the side opposite to that where the gas fill pipe is located. You must examine the vehicle’s underside to determine the exact location.

In an MVA, first confirm that the vehicle involved is a hybrid. As with a conventional vehicle, follow standard procedures for such situations; do not approach directly from the vehicle’s front or rear until it has been disabled and immobilized so you will not be in the vehicle’s travel path if it should move. This is especially important for hybrids because they may seem to be shut off when they are actually in their “Ready” mode. Chock the tires, place the transmission in Park, and engage the parking brake.

Disabling a hybrid vehicle and its electrical system is relatively simple; most of these procedures should already be part of department policy when responding to MVAs. Hybrid vehicle manufacturers typically recommend one of two options for disabling the high-voltage system. Either one of these steps shuts down the hybrid electrical system. The first and easiest method is to shut off the ignition and disconnect the 12-volt battery. You should already be doing this with conventional vehicles to disable the occupant protection systems.

If you cannot reach the ignition for any reason, the second recommended method is to disconnect the 12-volt battery and pull the high-voltage system fuse found in the engine compartment fuse box. Since manufacturers do not use a uniform color for this fuse, if you can’t identify the correct fuse, just pull all the fuses in the box to ensure that you will remove the correct one. Keep in mind that this is not the in-line high-voltage fuse built into the high-voltage wiring itself but simply the fuse that controls electrical flow to open and close the high-voltage relays or engage the hybrid system.

Hybrid systems’ bleed-down times vary among manufacturers but are typically between five and 10 minutes. Consult the ERGs for the vehicle you are dealing with for the specific time frame. Although disabling procedures will shut down the voltage flowing through the electrical cables, they do not bleed down the power from the high-voltage battery, which will remain energized.

Standard MVA response procedures designed to control vehicle movement and safety occupant protection systems will also control safety concerns posed by hybrids. If these procedures already exist in your organization, then you are already addressing the bulk of the concerns present when dealing with a hybrid.


Although most response procedures for handing incidents involving hybrids are generic, you should be aware of specific items regarding several models. Some models provide battery service disconnects that you can access to ensure that hybrid system power has been shut down.

In the Ford Escape, Mercury Mariner, and Mazda Tribute, there is a battery service disconnect on top of the battery under the carpet in the cargo area. In the Nissan Altima, the disconnect is in the trunk on the passenger’s side behind the rear seat. For the Chevy Tahoe and GMC Yukon, the disconnect is under the second-row seat on the passenger’s side (photo 9). The battery disconnect for the first-generation Chevy Silverado and GMC Sierra is under the rear seat on the passenger side of the vehicle. Do not use these battery disconnects if the battery is damaged; in that case, only an experienced technician should attempt to operate the disconnect.


The treatment of these disconnects varies among the manufacturers. Some manufacturers do not indicate the location of the disconnect in their ERGs. Some recommend using special “hybrid vehicle gloves” when operating the disconnect. Be sure to reference the ERG for that specific model. Use these disconnects as an additional option to “safety” the system after using the standard shutdown methods addressed above.

Ignition key systems on certain hybrid models may also differ from those to which you are accustomed. The second-generation Toyota Prius uses a key fob the driver inserts into a slot in the dashboard instead of a conventional key. (Once you insert the fob, you must depress the power button on the dash to start the vehicle.) Another system, optional on the Toyota Prius but standard on the Toyota Camry, Nissan Altima, and Lexus 450h, is the “intelligent” proximity key system. Once this key is within the proper range of the vehicle, the user can open the locked doors and, if the dashboard power button is depressed, it will allow the engine to start. To disable the ignition system and prevent the vehicle from being accidentally started, move this key far enough away so the vehicle cannot detect it. Although some newer models have shorter activation distances, the proximity key should be moved, at a minimum, 16 feet from the vehicle to prevent it from starting if the power button is inadvertently depressed. Ensure that all keys are removed from the vehicle; a passenger could also have a key. Of the models mentioned above, only the Toyota Prius is equipped with a disable feature for this system; it is on the dash under the steering column.

You can find additional specific items for other hybrid models by referencing their respective ERGs.


Emergency responders frequently express concern regarding applying water to a hybrid vehicle fire. Hybrid vehicle fires can be fought in accordance with the National Fire Protection Association and the National Fire Academy recommended practices for vehicle fires; as such, water is the most suitable agent for extinguishment.

This concern arises from the perceived potential for electricity to travel down the hose stream and cause an electrical shock to firefighting personnel. Although dangerous, DC power, unlike the AC power sources commonly found in buildings, does not seek a path to ground. Since DC electricity follows a path out from the battery, along the electrical circuit and back to the battery, the electrical current will not travel up the hose stream as it could from an AC power source. Hybrids using any type of AC power system incorporate a ground fault circuit interrupter (GFCI) to immediately shut down the power should there be a short. This operates on the same principle as your kitchen and bathroom GFCI outlets, which are designed to shut down should an appliance plugged into it come in contact with water.

Generally, a standard offensive attack is recommended unless the NiMH battery pack is on fire. If this is the case, live fire testing indicates that it is better to allow the battery to burn out rather than to attempt extinguishment (defensive attack). First, it is nearly impossible to get enough water directly onto batteries because of their protective shell. The only real access for water to the battery pack is through the battery vent, and many vent designs do not allow easy access for this.

Second, if the firefighter allows the battery pack to burn out, it negates the concerns regarding the hazmat properties of the residual electrolyte. Always make sure that the battery pack is cooled down enough to prevent reignition prior to releasing the vehicle. A thermal imaging camera can be a valuable tool to determine if the battery pack is cooled down in vehicles where the battery pack can be accessed visually.

If a defensive attack is warranted, pull back to a safe distance and use a water stream to protect exposures and control the path of smoke. If the situation does not allow for a defensive attack, such as if the vehicle is in a garage, take appropriate offensive actions.

Never overhaul high-voltage components since there is no guarantee that the system is deenergized. The effects of fire can render system safeties inoperable. Live fire testing indicates that these components can remain live after exposure to fire.


It would be rare to see a catastrophic crash sufficient to breach both the battery pack case and the individual batteries. Since the electrolyte is absorbed into the cell plates, it does not normally spill or leak, even if the battery is cracked. If the battery is crushed, it is possible that a small amount of electrolyte would leak (a few drops). Avoid any contact with the electrolyte because of the potential for human tissue damage. If necessary, contact CHEMTREC® [(800) 262-8200, www.chemtrec.com] for the batteries’ material safety data sheets (MSDSs). Toyota, Lexus, and Nissan ERGs contain information regarding neutralizing a battery leak and first-aid treatments for electrolyte exposure. In the unlikely event there is battery leakage at the site, local hybrid car dealers can identify appropriate cleanup contractors.


In the case of a submerged hybrid, manufacturers recommend removing the vehicle from the water and using standard disabling techniques. There is no risk of electric shock from touching the vehicle, whether it’s in or out of the water. Do not touch high-voltage components or cables. Hybrid ERGs typically address submerged hybrid vehicle concerns.


The following two incidents highlight some considerations in dealing with hybrid vehicles.

Incident 1. This accident occurred on a winter night when the driver of a Ford Escape hybrid lost control after hitting a patch of ice and collided with a telephone pole. Because of the angle of the impact, neither the frontal or side impact air bags deployed (photo 10). Likewise, the high-voltage hybrid system did not automatically shut down. The driver exited the vehicle but did not shut off the ignition, since the engine was no longer running. However, the vehicle actually was in its “Ready” state, and the engine started up a few moments later when the hybrid system most likely recognized the battery needed charging. On realizing the vehicle was still running, the driver proceeded to shut off the vehicle’s ignition.


Had the vehicle struck and bounced off the telephone pole and the driver exited while the vehicle was still in gear and in its “Ready” mode, the hybrid most likely would have begun to move on its own even if the engine was not running. The telephone pole prevented any further vehicle movement until it was shut down. This illustrates the concept that although a hybrid vehicle may appear to be “off,” it could just as easily be in its “Ready” state. Always approach such a vehicle with caution.

Incident 2. This accident, involving two tractor trailers and a Honda Civic hybrid taxi, occurred on a major Connecticut highway last spring. At the time of impact, the driver was the only person in the hybrid. The tractor trailer in front of the taxi and the taxi itself were stopped in traffic when another tractor trailer struck the taxi from behind, pushing it underneath the first one (photo 11). The force of the impact was so great that it lifted the rear tires of the trailer off the ground. The only hybrid indicator on the vehicle exterior was the badge on the right side of the trunk lid. The force of the impact damaged this area heavily; the badge was almost invisible. Only through keen observation did firefighters working at the scene identify the taxi as a hybrid.

11) (11-12) Photos by Kevin Cooney.

Firefighters on the scene stabilized the vehicle and the trailer and extricated the patient through the vehicle’s passenger side (photo 12). Disabling the hybrid system proved difficult because of the lack of access to the 12-volt battery and the initial issue in getting access to the ignition key. However, this model featured a Honda mild hybrid system in which the high-voltage cables are energized when the vehicle is accelerating or decelerating or when the air conditioner is on (if the unit is powered by the high-voltage battery). In this case, none of these conditions applied; hence, the only high-voltage power present was in the battery itself. The hybrid vehicle presented no unusual obstacles to victim removal than would have been found on a conventional vehicle.


Although this vehicle sustained heavy rear-end damage, the battery pack remained intact, with only a slight dent in the external case, which did not affect the battery module. This shows that, in most collisions, the battery case would not be destroyed.


As consumers continue to purchase hybrid vehicles and manufacturers introduce new models, firefighters must continually educate themselves on handling responses to hybrid vehicle incidents. Chief officers should modify existing department SOPs to address hybrid vehicle issues. Once again, as long as first responders are educated and adhere to proper safety procedures, they need not fear hybrid vehicles.

Manufacturers have produced ERGs to educate responders about hybrids. These valuable resources are readily available on the Internet from a variety of sources or from the individual manufacturer Web sites. Departments should make these guides and formal training available to their members to ensure that they get the proper information. As always in the fire service, proper education is paramount.

JASON D. EMERY is an 18-year veteran of the fire service, serving the past 14 years with the Waterbury (CT) Fire Department, assigned to the rescue/hazmat company. He has a bachelor’s degree in fire science from the University of New Haven. Emery is a certified fire instructor, has taught extensively on hybrid vehicles, and is an FDIC presenter. He founded Emergency Training Solutions, LLC, and is the lead PowerPoint® designer for Fire Engineering’s Handbook for Firefighter I & II (Fire Engineering, 2009).

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