Fires in vehicles that are powered by alternative fuels when they are in underground facilities, such as tunnels and garages, involve new risks for the rescue services and society. Jonatan Gehandler, researcher into fire and risk at the Swedish Research Institute, RISE, has produced a report summarising the current state of knowledge.
What are the special problems involved with fires in alternative fuels?
“In vehicles powered by compressed natural gas or hydrogen gas, the fuel is under high pressure, several hundred bar. Weakened containers or safety systems that do not manage to react lead to an increased risk for explosion in the case of a fire. Regarding electrical cars, the fumes from a burning battery release substances about which we do not yet know much. A burning electric car also needs cooling for a long time because the battery generates heat all of the time. This means that the fire can easily blaze up and accelerate again. Hydrogen gas burns with a colourless flame, which means it is hard to detect the fire. Moreover, it is odourless. Motor gas can lead to a BLEVE, an explosion where the heated liquid rapidly vaporises, after being heated by fire.”
Are there new risks for the rescue services?
“Yes, an increased risk for explosion in a gas vehicles, of course, makes the work for the rescue services both more difficult and more dangerous. The fact a car is powered by gas is often indicated solely by a small logo on the tailgate or not at all. There is an ongoing standardisation process within the CTIF (International Association of Fire and Rescue Service) to identify vehicles with alternative fuels. The CTIF is an organisation working for the international exchange of experience in the fields of fire protection, disaster assistance and rescue. For fires in underground garages, which rapidly fill with smoke, it is very difficult to find out what fuels power the cars. Today, the personnel in the rescue services are very careful if they suspect there is a gas vehicle involved in a fire both above ground as well as below ground.”
How is society affected in general by the new risks?
“If there is no life to save, the rescue service will adopt a defensive strategy. A burning gas vehicle may mean that streets and public spaces must be cordoned off. Clearly, this results in increased costs.”
What importance does the garage and underground facilities in question have?
“The primary problem is that the rescue efforts frequently must be carried out in smoke, which makes the situation difficult to grasp, at the same time as there are risks for a building collapse. Today’s systems for demand-controlled ventilation are suited for traditional fuels such as petrol and diesel. In other words, a leaking gas car will not be detected by the sensors. The same applies for toxic gases that are emitted if a battery goes into thermal runaway. Guidelines needs to be adapted to this new situation now.”
Are any checks made on the containers in gas vehicles today?
“Not in Sweden in all cases. It is true that our cars are inspected periodically, once they have passed a given age. However, the containers are not checked. This would require visual inspection to detect corrosion or damage.”
Alternative fuels are advancing on a broad front across the entire automotive industry. How high is the level of consciousness in the industry, such as the vehicle manufacturers, regarding the risks associated with alternative fuels?
“I believe that they are aware of the risks since they are developing these systems but, taking into consideration the fact that there is a clear potential for raising the safety for these systems even further, we have not yet come the full distance. MSB, the Swedish Civil Contingencies Agency is attempting in various ways to urge the safety process forwards, but currently we get the impression that the will to push the safety process forwards is lacking among the other actors.”
Will your research work go further?
“Yes, we will try to understand why safety valves sometimes fail in preventing an explosion. We will start from scratch and study the way empty gas containers behave during a fire. Different scenarios will be studied and there will be practical fire trials in our laboratories. Among other things, we want to study how the temperature spreads in the container with different fire exposures. Steel and composite conduct heat differently. In 2018, we are planning for trials on an exercise field with CNG, Compressed Natural Gas, in the containers.”
Jonatan Gehandler’s study was financed by Nordiskt Vägforum (Nordic Road Association), which is an industry collaboration including members from both the private and public sector in Denmark, Finland, the Faeroe Islands, Iceland, Norway and Sweden.
The study can be downloaded from www.diva-portal.org/smash/get/diva2:1081095/FULLTEXT01.pdf
Top image: Figure 1 – Fire in a gas bus conducted as part of a reconstruction for the Swedish Accident Investigation Board.