We recently published a guest post about emergency evacuations from our colleagues at Graphic Packaging that mentioned the Mont Blanc tragic tunnel fire. Shortly after we published the blog, I had the opportunity to attend an SFPE webinar that focused on the fire protection design considerations of road tunnels, and I thought I would share a few highlights.

The webinar was presented by David Barber, Global Fire Engineering Leader, with Arup in the Australian Region. Mr. Barber began the webinar by stressing that fire safety is often a complex problem in tunnels and that the goals of fire safety design are twofold:

  • Prevention of fires from occurring in the first place; and
  • Prevention of fires that do occur from escalating to a major event

From 1995 to 2006, over 300 lives have been lost in tunnel fires. In addition to the Mont Blanc fire, where 39 lives were lost, here are a few other fatal tunnel fires that occurred between the years of 1995 and 2006:

Year

Tunnel

Casualties
1996 Isola delle Femmine (Italy) 5 fatalities; 20 injured
1999 Tauren (Austria) 12 fatalities; 40 injured
2001 Gleinalm (Austria) 5 fatalities; 4 injured
2001 St. Gotthard (Switzerland) 11 fatalities
2006 Viamala Tunnel (Switzerland) 9 fatalities; 6 injured

These unfortunate accidents resulted in fundamental changes in tunnel design and have allowed fire protection engineers to play a more significant role in the entire design process. By incorporating a greater use of performance-based design solutions and risk-based analysis, fire protection engineers can help achieve tunnel design goals that often include the reduction in the likelihood of accidents and fires, the reduction of evacuation time, provisions for firefighter and emergency medical services (EMS) intervention, and provisions for business continuity.

What Factors Should Be Considered in the Fire Protection Design of Road Tunnels

When designing fire protection solutions for road tunnels, Mr. Barber suggests asking the following questions:

  • What are the life safety goals and other objectives?
  • Which code(s) provides the framework?
  • Can a risk-based approach be used?
  • What is the acceptable level of safety performance?
  • How will the design be proven safe?

In addition, fire protection design for tunnels should not only focus on the prevention of fires, but also on the evacuation of occupants. Self-evacuation of occupants is critical for life safety. Designs must include a robust solution for self-evacuation that can include: spacing between exit doors; emergency lane width; auto detection systems; alerting through overhead signage, texts, and/or radio; directional distance signs to exits; clear exit signs; lighting; help points; emergency phones; smoke control; and suppression systems.

Smoke hazard management and smoke control systems play a huge role in offering tenable conditions for occupants to evacuate safely by providing positive airflow that limits the spread of smoke and allows for the extraction of smoke and heat. Tools like Computational Fluid Dynamics (CFD) models can be used during the design phase to better understand options for ventilation control and smoke hazard management, as well as to better determine critical velocity.

What about Fire Suppression Systems in Road Tunnels?

While fire suppression systems have been undoubtedly effective and efficient in the built environment, there are concerns when it comes to their use in road tunnels. According to Andreas Haggkvist in an article in Fire Protection Engineering, those concerns include: hindering the evacuation of occupants by the generation of steam that may cause injuries; difficulty in suppressing a fire that starts in an engine; and the potential for petroleum fires to continue to produce combustible gases after being extinguished that can create an explosive environment.

Despite these concerns, newer approaches to fire protection design are taking advantage of the use of suppression systems to protect the structural performance of road tunnels. Mr. Barber sited the Burnley Tunnel fire in 2007, where the deluge system activated instantly; helping firefighters to keep the fire under control and minimize structural damage, which allowed for the tunnel to reopen four days after the fire.

The Road to the Future

While road tunnel design has improved and evolved throughout the years, fire protection engineers still have a lot of work to do. Mr. Barber concluded that further testing is needed, including large scale testing, in regards to suppression systems, structural protection, occupant egress, and communication and control methodologies, and the influence of these factors on design strategies.

By Jeff Harrington, CEO and Founder of Harrington Group, Inc.