Tunnel: Incident Management & Fire Safety Systems



          Source: Firefighternation.com

The picture above shows the Swiss LRZ 08 fire fighting train, one of the most advanced fire fighting vehicles in operation today, which services the railways and tunnels in the Swiss Alps. The trains are packed with the latest state-of-the-art fire fighting equipment, and the 265 ton fire and rescue vehicle carries heavy lifting, spreading and cutting machinery for heavy rescue operations. On board is an air compressor which can supply 950 L/min of filtered air at a pressure of 300 bar. A water spray protection system consists of two cannons that have an output of 2,400 L/min of water, and a projection of 70 metres; 45 metres for foam. With fire fighting techniques and equipment ever improving, tunnel design must allow for good access for the emergency services as part of its fire safety planning.

One incident management system developed by FirePASS, involves using modified air to starve the fire of oxygen. While normal smoke evacuation naturally feeds the fire with oxygen, the FirePASS system feed the fire with oxygen reduced air that crucially provides a breathable atmosphere which has extinguishing properties. The system is installed on site and modifies the ambient air, to reduce oxygen levels to 14-16% depending on the risk factor associated with the tunnel. It is a highly effective solution to fires in closed tunnels, as it starves the fire of oxygen and lessens the chance of ignition of inflammable materials.

Automatic incident detection (AID) Systems are advancing all the time for use in tunnel design, and at some point in the future it is expected that this may become a requirement not just an option. They are typically video based and use advanced algorithms to analyse the images and detect any deviance from normal conditions. Linear heat detection systems and smoke detectors are used alongside video to report to operators as quickly as possible the location of the source of the fire. In addition these sensors are able to feed back critical information about the temperature, the smoke volume, and smoke characteristics to aid the best possible tactical response. Whilst not replacing operators or emergency services, the systems can automatically activate smoke ventilation systems, sprinklers and water mist systems, and initiate evacuation procedures.

Communication systems, both audio and video, are also becoming more desirable in design to aid evacuation. Research has shown that users are often reluctant to leave their vehicles and exit the tunnel as they may not grasp the severity of the situation, or believe that the emergency services will reach them before they are in any serious danger. Because of the heat and smoke which is so intensely and quickly produced in tunnel conditions, good communication to users of the tunnel can be considered an integral part of any management system.