Truck fires in a tunnel can create heat release rates (HRR) significantly
higher than 100 MW. Because of a fast spread of smoke and heat the self-rescuing
period is shortened significantly. Furthermore, it was experienced that
firefighters are not able to approach the fire because of enormous heat and
radiation. As consequence, the fire may spread to adjacent vehicles, which is
reported for distances of more than 50 m. Tunnels can be damaged severely by
fires and the repair works causes long closing time of tunnels. In addition to
direct costs for the refurbishment of the tunnel, further economic losses will
occur due to the closure time.
Conventional deluge systems in Japanese and Australian road tunnels have been
known since the 1960s. During the last years the research work was concentrated
in the development of more effective and cost-effective solutions based on water
mist technology. Orientating fire tests as well as specifications of minimum
requirements were carried out within the European research project UPTUN.
This basic work was extended by the safety of life in tunnels (SOLIT)
research project, funded by the German government. The scope of SOLIT was not
only to study the effects of water mist fire suppression systems in tunnels, but
also the interactions with other safety systems, such as fire detection, passive
fire protection or ventilation. Furthermore, the integration of active fire
suppression systems into a holistic tunnel safety system was part of the work
Within this research project a large-scale fire test program with more than
50 fire tests, including 25 truck fires with a potential HRR of almost 200 MW,
was carried out in the test tunnel of San Pedro des Anes (Spain). Furthermore, a
two-week testing and training period with the Madrid Fire Brigade was carried
out after the SOLIT program.
Two fundamental results were
achieved during the fire tests:
Primarily, water mist systems are able to control the HRR
of fires in tunnels, so the atmosphere will be improved significantly. Hazardous
effects of toxic smoke on people will be reduced and due to the reduction of
temperatures and radiation, a firefighter’s approach is improved significantly.
Furthermore, the fire spread will be hampered and the thermal load on the
building structure also be reduced.
Secondarily, due to positive interactions with the ventilation system, the
effectiveness of a tunnel ventilation system, longitudinal as well as
semi-transversal, is increased significantly.
Based on the results of the SOLIT research project, a water mist system was
applied into several parts of the M30 tunnels in Madrid. As a basic principle
the technical equipment and the methodology of implementation comply with the
UPTUN 251 guidance, recommending minimum standards for water-based fire
suppression systems in tunnels.