Alternative Fuel Vehicles and MVCs

We all know about alternative-fuel vehicles, and when we typically think about this type of automobile we think of electric or hybrid vehicles. But there are other alternative-fuel vehicles traveling our roads as well. In some parts of our country, they are more prevalent than in other areas. These vehicles are powered by compressed natural gas (CNG) and liquefied natural gas (LNG), and they have become a new concern for first responders.

Today, there are various types of these vehicles operating on our roads, and proper training of first responders is imperative so that we are safe on scene when the call goes out for a motor vehicle accident (MVA) involving vehicles powered by these types of fuel. The question: Are you knowledgeable enough to be able to recognize these vehicles and make the scene safe when at an accident where they are involved? Hopefully, after reading this article, you will be.

Tank Design

The first thing we must understand is that, barring any catastrophic accident, the CNG tanks that are being used today are safe. They are classified as Type 4 cylinders, which are very similar to the self-contained breathing apparatus (SCBA) that we use in the fire service. The difference is the size of the cylinder and the pressure to which it is filled. Our SCBAs are filled to 4,500 psi while the CNG cylinder is filled to a max of 3,600 psi.

The tanks have gone through rigorous testing that includes dropping the tank from a predetermined height and hitting the ground in all possible directions and having a rifle fired at the tank (which causes the gas to escape without exploding). Each tank has a pressure relief device (PRD) that will vent the gas once the temperature of the tank reaches 206ºF. To test the PRD, the tank is placed in a bonfire; when the tank reaches this temperature, the PRD opens and releases the fuel through a vent tube, preventing an explosion.

With pickup trucks, the tanks are at the front of the truck bed in a housing protecting them from the elements. You may also find this with other types of vehicles, including vans. You may also find the cylinders inside or underneath the vehicle between the frame rails. With the Honda Civic, the tank is in the trunk of the vehicle, and the vent tubes for these vehicles can be underneath the vehicle.

Vehicle Identification

When the tones are dropped for an MVA, we have to start our scene size-up before we hit the apron of the firehouse. We ask: What are we going to find? What type and how many vehicles are involved? How many victims might be injured? What other resources are needed? Now, with today’s alternative-fuel vehicles, we must also determine what type of power/fuel source these vehicles are using before we start our extrication of the victims. With our scene size-up, we need to look for the CNG or LNG blue diamond logo that is used on these vehicles.

The logos will be seen on the rear of the vehicle, with the right rear being the most prevalent location. You may also find logos on or near the refueling ports and fuel tanks. In the case of the Honda Civic, there is the term “natural gas vehicle” on the lower part of the rear doors; this signifies it is a CNG-powered vehicle, as Hondas are only powered by CNG. Pickup trucks from Ford, General Motors, and Dodge are bi-fueled vehicles that use either gasoline or CNG. Semitrucks are powered either by CNG or LNG, as there are limited bi-fuel trucks available at this time.

The largest concern for first responders nowadays is whether the vehicles involved in a MVA are gas, diesel, or CNG/LNG fueled. The Honda vehicle is relatively easy to recognize, but the semitrucks will be our most difficult to identify. For a semitruck, the logos are placed on the right rear of the cab. While this information lets you know where to look for the logo on a semi, the problem is that semis are traveling the roadways with trailers attached to their fifth wheel, which will hinder our view of the logos. These trailers only leave approximately four to five feet between the front of the trailer and the rear of the cab, making it more difficult to spot any logos.

Semi tractors can have their CNG cylinders placed behind the cab in a protective housing. The cylinders can be placed either horizontally or vertically, in a configuration of either three or four cylinders. Some semi tractors will also have a saddle tank on the right side of the vehicle, giving a total of five cylinders. They can also have only sidesaddle tanks if they so choose. Straight-axle trucks will have saddle tanks, and if the truck is a LNG truck then tanks are also sidesaddle.

Vehicle Shutdown

Regardless of the type of vehicle, the process for shutting down a CNG/LNG-powered vehicle should be straightforward. Turn the key off and disconnect the 12-volt battery by cutting the positive and negative cables. Once the 12 volts are removed, the fuel delivery can be interrupted. In the case of over-the-road trucks, locate the refueling port and turn the “red’ handle a quarter of a turn to stop the flow of fuel.

In the case of an LNG vehicle, there is a red gate valve handle that you will turn to stop the flow of fuel to the engine. Remember to use proper personal protective gear when dealing with LNG-fueled vehicles as the fuel is at -260ºF, posing a danger to exposed skin. Fuel lines that have frost on them have LNG flowing through them.

If the truck involved is a CNG truck and you are unable to get to the emergency shut-off valve because of a rollover, each cylinder will have a manual shut-off valve you can close. These valves are gate valves you will have to turn to stop the flow of fuel. The configuration and location of the cylinders will dictate how you will access the valves.

On waste-hauling trucks with compactors, the manual shut-off valves are on top of the compactor in a “dog house” with an oblong hole for each valve. There are some waste-hauling trucks that are considered long-haul trucks that also have a sidesaddle tank on the right side of the vehicle. This tank will also have its own shut-off valve and possibly a manual shut-off valve.

If these vehicles are involved in an MVA where there is a chance of leakage of CNG from the fuel tank, first responders should hear a hissing sound as the fuel is being released, along with the smell of mercaptan, which makes it easy to detect a gas leak.

First responders should be aware that not all over-the-road trucks are using CNG fuel with mercaptan in the fuel. It is possible that the trucking company is producing its own CNG from waste products to fuel the trucks. If this is the case, it is not required to add mercaptan to the fuel. If fuel is leaking from the PRD or from the tank, first responders should allow the fuel to vent until depleted. Note: LNG fuels usually do not have mercaptan added to them.

In case the PRD is releasing fuel, and that fuel has been ignited at the end of the tube, responders should allow the fuel to continue to burn and protect the exposures of the trailer and other items that maybe exposed. The length of time that it will take to deplete the fuel in the tanks will depend on the size of the tank and the amount of fuel it contains. Various locations for the vent tubes depend on the type of vehicle and the location of the tanks.

Road Awareness

CNG and LNG vehicles are traveling our roads today and will be increasing in numbers as the number of refueling stations increases. Additional types of alternative-fuel vehicles will be also be available as new technology is introduced.

As first responders, it is our responsibility to be educated on these new technologies and how we will safely handle these MVAs when we get the call.