Commercial vehicles utilize pneumatic controls for various devices on the truck. It can be used for climate control settings, wipers, split-shift transmissions, starting systems and suspension/cab ride systems. However, the primary function is the vehicle braking system. Air will be necessary to both release and apply the brakes for the vehicle. There will be a dual air system in these vehicles; the Primary Air System is used for braking, and the Secondary Air System will run other functions on the truck. Keep in mind that if the primary system was to suffer a catastrophic failure (leak), the secondary system will provide enough air to control the braking system for about a minute. After about a minute, as the air exits the vehicle, the brakes will begin to apply by themselves. On the fire scene, all of these components are charged with compressed air and are potential explosion hazards (see Photo 6).
Vehicle Fire Response
First, upon receiving a dispatch to a fire that involves a large commercial vehicle, be sure that the right resources are responding as soon as possible. Many companies utilize an automatic aid system that will provide for notification and dispatch of multiple companies to the incident. Be sure to make contact with a response-capable heavy wrecker company; in the event of an under-ride or rollover incident involving passenger vehicles and commercial vehicles, a heavy duty wrecker with a rotating boom assembly would prove to be advantageous on the scene. Coordinate these resources with local law enforcement, as many police departments have these resources categorized and “on-standby” to respond to major roadways in your response area. Be sure to notify them immediately upon arrival if you think that their services might be needed.
There will be significant potential for an increased hazardous material release risk. Most times, when dealing with passenger vehicle fires, the fuel system will remain somewhat intact; there may be a leaking fuel line, but for the most part, it will be able to be controlled with minimal additional resources. Commercial trucks, however, pose a larger risk. Notwithstanding the materials that are being transported, most large tractor trailers can carry upwards of 300 gallons of fuel in dual saddle tanks directly under the cab (see Photo 7). Not only is this a potential explosive issue, but it may require your rescuers to work directly over the product when it is released onto the roadway.
Initial arriving units must be able to answer one major question: What is in the compartment? From local distributor deliveries, to nationwide long distance movers, the type and amount of fuel in a container can be staggering. These vehicles can have just about anything in their container, and can react surprisingly when they are heated (see Photo 8). The urge to treat these incidents as a “vehicle” fire must be resisted. A single company response to this “vehicle fire” is not efficient and puts crew members at significant risk; the first alarm should include two engine companies and a ladder company for adequate manpower and resources. Overhauling and removing the contents will be manpower-extensive; call for a lot of help early on.
Like any other compartment, coordinated ventilation and suppression need to be implemented. Ventilation from the top is the method of choice, but standing on top of a vehicle to cut a hole in the roof can be extremely hazardous; many vehicles do not have significant support in the roof area, and the amount of heat energy being generated into the roof will result in extreme exposure to the firefighters (Photo 9). For this reason, the vent point should be opened from an elevated device, preferably a tower ladder. If one is not on the initial alarm, one should be added to the assignment whenever a commercial vehicle is involved in a fire. Once ventilation is underway, suppression forces must be at the ready. Making the attack can come from a few avenues; piercing nozzles have shown to be effective on some vehicles, depending on construction. Lighter materials will be easier to penetrate with these appliances. However, shipping containers and intermodal trailers can prove to be tough to cut for suppression (see Photo 10). Controlling the doors at the rear may be the best option. When operating from the door, control the door opening. Crack the door just enough to allow the stream to enter the upper areas of the compartment. Use of Class A Foam for this application can be a significant benefit in limiting time of extinguishment; remember, you are having this compartment fire in a roadway, not in a house. Once the initial knockdown is made, many times complete extinguishment will require a significant amount of overhaul. Get off the road as fast as you can, keeping traffic flowing and limiting the risk to your firefighters.