Multiple Hazards of Vehicle Fires
|Editor's note: Vehicle fires nowadays present a variety of dangers to firefighters. As well as the following Michael Lee article, check out Hybrid Hazards Present New Challenges from last year.|
Photo Tod Parker/Phototac.com
Firefighters tackle a car blaze in Indianapolis in 2006.
While they're more prevalent than structural fires, we tend to take such operations more lightly unless the vehicle is parked in a garage.
Reported vehicle fires in the United States averaged 325,100 annually from 1999-2003, according to the NFPA statistics, These fires were the direct cause of an average 440 civilian deaths, 1,500 civilian injuries and $1.2 billion in direct property damage. It goes to show we should never be complacent when it comes to fighting these fires.
These statistics make interesting reading. The primary causes of highway vehicle fires during this period were mechanical or electrical failures, which accounted for nearly 75 percent of the total. However, only 9 percent of these types of fires caused deaths. Vehicular collisions or rollovers caused 3 percent of highway vehicle fires, but resulted in 58 percent of the deaths. About two-thirds of the highway vehicle fires began in the engine, transmission or wheel area. Meanwhile, only 2 percent of highway vehicle fires started in the fuel tank or fuel line area, but these fires caused 17 percent of the associated deaths. Young adults and older teens are considered the at-risk age groups for vehicular fire deaths and injuries. In addition, one-third of non-fatal highway vehicle fires injuries occurred when civilians attempted to fight the fire on their own.
Hazards, safety impacts
Different vehicles carry varying degrees of safety impacts based on their size, manufacture and their utilization. Automobiles have evolved into lightweight structural support systems covered in plastic and false veneer panels on the inside. Newer vehicles now generate more toxic smoke can contain carbon monoxide (CO), hydrogen cyanide (HCN), hydrogen chloride (HCL), acrolein (CH2CHCHO). Don't forget that commercial vehicles will carry products based on their profession or responsibilities — construction, plumbing, electrical, medical repair, etc. — which will have by-products when alight. Remember also that large recreational vehicles can be towing a smaller vehicle as well. A further hazard to consider is the fact vehicles can be parked and utilized as temporary methamphetamine labs.
For years we have had to deal with only a few types of fuel when it comes to vehicle fires, specifically flammable gasoline products and combustible diesel. Then in the 1990s, we started to experiment with other fuels such as propane and natural gas, and had to learn to look for vehicle fuel identifying labels. Now we have to contend with a whole new range of fuels, and E85 and its polar solvent impacts brings a new player to the field. And while hybrid vehicles may not use differing fuels, should their high voltage protection covers melt off from fire, do you know what the 300-volt system will contribute to a vehicle fire scenario?
Fighting hydrogen gas fires
The next fuel on the horizon is hydrogen gas utilized for fuel cell technology. While this new energy source hasn’t fully taken off yet, they are starting to crop up in California and other places. Compressed hydrogen fuel tanks will operate under high (5000–10,000 psi) pressure and will be subject to potential failures associated with pressure vessels under heat/fire related stresses. There have been reports of high-pressure hydrogen leaks igniting for no apparent reason, and several ignition mechanisms have been proposed. Current analysis has not solved all the reasons for spontaneous fuel leakage. Hydrogen is a flammable, colorless, odorless and compressed gas packaged in cylinders at high pressure. It poses an immediate fire and explosive hazard when concentrations exceed 4 percent. It is much lighter than air and burns with an invisible flame.
MSDS sheets list the following firefighting instructions for hydrogen gas fires:
Special firefighting instructions: Evacuate all personnel from danger area. Immediately cool container with water spray from maximum distance, taking care not to extinguish flames. If flames are accidentally extinguished, explosive re-ignition may occur. Stop flow of gas if without risk while continuing cooling water spray.
Unusual fire and explosion hazards: Burns with a pale blue, nearly invisible flame. Hydrogen is easily ignited with low-ignition energy, including static electricity. Hydrogen is lighter than air and can accumulate in the upper sections of enclosed spaces. Pressure in a container can build up due to heat, and it may rupture if pressure relief devices should fail to function.
Other vehicle fire impacts consist of the construction elements of the vehicles themselves:
- Drive shafts are closed hollow tubes and can rupture when heated
- Battery (or batteries) can explode with acid being released
- Struts used to keep hatchbacks and engine hoods open can explode during fires
- Older vehicles with energy absorbing bumpers contain pressurized shock absorbers that can burst under heat impingement
- Fuel injection systems vaporize fuel into cylinders; that fuel is still under pressure when the vehicle is at rest
- Air conditioning systems contain compressed refrigerant gases
- Tires are pressurized as well as fuel tanks.
Finally, remember that vehicles are being built more sound resistant these days. This means they retain fire gases under pressure for longer periods of time before the windows fail, which can result in an explosion hazard.
When responding to vehicle fires, gather as much pre-arrival information as possible to assist in matching resources with possible impacts. A good example would be a vehicle fire on the side of the road versus a vehicle fire in front of fuel pumps at a gas station. What types of structures are close to the vehicle? Are there other vehicles as exposure adding to the total fuel load of the event? What types of traffic impacts will your crews have to deal with while extinguishing the fire? Will some type of crowd control be required? And finally, what other hazardous materials are on scene or in the vehicle that could cause injury or a fatality in conjunction with the fire?
Remember to carry out strong PPE safety practices when operating at vehicle fires. Full protective clothing and SCBA should be utilized on all vehicle fires! While booster lines were somewhat effective in the past for extinguishing, the vehicles of today are manufactured with larger amounts of plastic. These molded plastics drastically increase the BTUs generated by a vehicle fire. As the total amount of fire volume today is nearly twice that of 20 years ago, larger attack lines from the onset are called for. I recommend a minimum 1 ½" line and the utilization of a 1 ¾" line from the start. If dealing with a large van, bus or semi or if the vehicle is hauling a significant amount of combustible material, utilize a back-up line for protection.
Also consider a water supply line for larger vehicles. You should approach it from upwind and uphill if possible and always from the corners of the vehicle; if there are compressed gas cylinders in the bumper or if the tires are ready to burst, you put yourself in a place where injury is reduced. Attack fire on the ground first and sweep away from the attack team. When possible, place chocks to prevent vehicle movement — our department once had a vehicle that shorted out the starter, which meant it kept trying to start the vehicle. It moved it in 3-5 ft bursts and forced us to fight a moving vehicle fire. Consider the use of foam to accelerate the extinguishment of the fire.
When the fire is contained in the engine compartment, access should be gained by use of the hood latch if possible. If not, consider breaking out a headlight and applying the stream through the headlight assembly or grill area. You may also bounce the hose stream off of the pavement into the engine compartment to reduce the volume of fire in the engine until the hood can be opened.
Various methods exist to open the hood of the vehicle on fire; the key is to ensure that the hoseline crew is ready to extinguish the fire when the hood is opened. Ensure it can be kept open through the use of a halligan tool or some other method. Apply water to the engine, interior and dashboard area as necessary. Gain access to the trunk area to check for extension if it is not obvious that there has been fire extending into the trunk. If unsure, use a forcible entry tool to break out a taillight to confirm. If needed, this same taillight hole can be used for suppression until the trunk can be opened manually. Ensure all compartments are opened and visually inspected including engine trunk and interior. Remember to overhaul the vehicle to prevent rekindles. Pull the interior moldings, remove cargo from the trunk and if required remove seats.
Fighting vehicle fires are generally straightforward, quick fires. But remember that these types of fire can take the lives of people through complacency — usually ours. Be familiar with vehicle construction and the hazards they present. Be cautious of cargo you can't see. Learn new vehicle fuel types, impacts, fire hazards and required suppression methods. Choose the right size line to put the fire out quickly and lastly — wear all your protective gear!