Current requirements to transportation tunnels provide a unique challenge to designers, users, and the emergency services personnel. Fire safety of tunnels tends to be the limiting factor in increasing their length and traffic load. Enhanced fire-safety requirements shall also meet the growing threat of terrorist attacks and sabotage. This is especially important for the designs of new strategically important tunnels. Recent tragic events in traffic tunnels call for establishment of a new, higher level of fire safety both for tunnel designers and operators. It is recognized that the two main goals of tunnel safety are to:
Compared to open roads and railways, statistics show that the risk of accidents is lower in tunnels. This is primarily due to the minimum effect of weather conditions, speed limits, steady lighting, and the absence of junctions. However, even small accidents are difficult to manage in tunnels, particularly for rescue personnel because of their very restricted access. As experience has shown in the automobile tunnel fires, the flame in Heavy Goods Vehicles (HGV) fully develops in 5 – 10 min., with an intensity of 50 - 100 MW or more [1, 2]. The release of such a large amount of heat energy prevents firefighters from even entering the tunnel. Therefore it is recommended to start fire extinguishing during the first 5 minutes after fire initiation. This requirement cannot be fulfilled by current tunnel fire suppression systems and technologies.
The multiple tunnel fire-safety problems can be solved by using FirePASS' approach in tunnel fire suppression, and specifically by application of a fire-suppressive or fire-preventative, premixed hypoxic (nitrogen-based or oxygen-reduced) total flooding agent, which has a precisely controlled oxygen level that is safe for humans. Such an agent can be produced in effluent quantities on-site from ambient air, and can be stored for instant fire-suppression, and/or the creation of a permanent human-breathable, fire-preventative atmosphere in tunnels