Deep Heat: Protecting Against Fire in Tunnels

16 November 2009 (Last Updated November 16th, 2009 18:30)

An outbreak of fire in a rail tunnel can have disastrous consequences. Daniel Garrun finds out how prevention is better than cure as Arena International's Fire Protection & Safety in Tunnels conference gets underway in Paris.

Deep Heat: Protecting Against Fire in Tunnels

One of the most terrifying scenarios for any underground railway passenger must surely be the outbreak of fire deep in the constricted bowels of a rail tunnel network. To address this challenge, experts from all over the world will gather at Arena International's Fire Protection & Safety in Tunnels November 2009 conference in Paris.

As the event kicks off, Bombardier lead engineer of materials David Tooley spoke with railway-technology.com's Daniel Garrun to find out what prevention and crisis strategies can be employed in the event of a tunnel fire.

Daniel Garrun: What makes a fire inside a train tunnel a uniquely dangerous situation?

David Tooley: The risks caused by a fire inside a tunnel are greatly increased where even a minor fire or smoke can cause panic and resulting injury.

Passenger doors may not be available and escape from a tunnel is also much more difficult. In addition, smoke builds up quickly because there is little or no fresh air coming into the compartments.

DG: What are the main factors when considering how to prevent fires in such a challenging environment?

"The risks caused by a fire inside a tunnel are greatly increased where even a minor fire or smoke can cause panic and resulting injury."

DT: The primary factor is infrastructure – trains and operators working together to manage the risk.

Trains must be built to the latest design engineering standards with features in place to stop fires occurring. Adequate ventilation, reliable communication devices and having highly trained people at hand are also extremely important.

DG: How can the design of a train or carriage improve safety in the event of a fire?

DT: The rolling stock designer and manufacturer should use materials that have low ignitability, flame spread, smoke and toxic emissions. Effectively implemented design elements can ensure that a significant ignition source is needed to cause a fire, which can then usually be limited to within the capacity of strategic ventilation systems.

Research is now underway to develop a design code for trains as well as to model toxic gas emissions development from a fire onboard a train.

DG: How can trains be built to complement the safety measures already incorporated into the design of tunnels?

DT: Interaction between designers and train designers is key. System designers need to install suitable ventilation systems to manage the effluent from a train fire and train designers must build to minimise risk, including stopping trains in the tunnel and making sure that trains are not disabled. Designers also need to make sure there are suitable places of safety and evacuation routes.

DG: Is it possible to predict how a fire moves in a tunnel and how could you use this information to improve safety?

DT: Computer modelling capability has progressed in recent years. Programmes such as NIST Fire Development Simulation, BRE Jasmine and others can model the development of fire scenarios in many different systems. These have often used the output from train fire simulation runs as the input.

"The designer and manufacturer should use materials that have low ignitability, flame spread, smoke and toxic emissions."

DG: The management of heat release is often spoken of as key to managing fires. What does this mean exactly?

DT: Rate of heat release is a measure of fire size, allowing comparison of the risk from different fires, which is essential to managing them. Passenger safety is only at risk if the fire event exceeds critical parameters. Until this critical stage is reached, people have the opportunity to move to a place of safety.

DG: How important is it to set global standards of fire safety?

DT: Without a common set of engineering standards, local designers and manufacturers worked to local standards even though the consequences of a train fire are the same globally.

Modern transport systems such as the Channel Tunnel link cross different countries so a means of ensuring standards are consistent is very important.

Local cultural issues, however, mean that every design solution requires review for local conditions. For instance, reactions to fire management systems may vary, making it essential to still keep room for local variations.