Iain Cumner, Managing Director, Patol Ltd, looks at tunnel fire safety

Though thankfully relatively infrequent, fires in tunnels remain high profile given the potentially catastrophic consequences that can result.

A look at just some of the major incidents that have occurred over the last 30 years and the resulting fatalities highlight why protecting tunnels continues to be vital: 1995, Baku Subway (289 dead); 1999, Mont Blanc (39 dead); 1999 Tauern (12 dead); 2000 Kaprun (155 dead).

In addition to the risk to human life, fire can cause severe damage to a tunnel’s structure, often necessitating complete closure and the resulting serious economic problems that arise from the disruption to transport links.

This has intensified with the development of mass transit systems to accommodate population growth to ensure people are able to travel smoothly, both locally and globally.

Increased fire load

A fire within a tunnel can potentially involve several different components, including cars, trains and hazardous and structural materials, all of which can contribute to the fire load and the potential for rapid escalation of a fire.

The accumulation of combustible debris along the roadway and within vent shafts, along with fuel spills and oils on the road surface caused by motor vehicle accidents, can also contribute to fire risk.

Other potential ignition sources include short circuits and electrical malfunctions in control power cables, and ventilation and air handling equipment which has a vital role to play in the event of a fire.

A consideration for a fire detection and evacuation system is the limited access /egress points in a tunnel.

This means that fire systems need to detect at the earliest opportunity to allow evacuation to designated safety muster points and enable swift tackling of the fire itself.

Patol is a UK based company that is part of the Sdiptech Group.

It is has more than 50 years of experience in developing, manufacturing and supplying fire detection systems for a wide range of applications, including tunnels.

Amongst the applications for which Patol has supplied a fire detection solution is the Al Rough Tunnel, part of the $650m Khorfakkan to Sharjah Road and Tunnels Project, one of the most significant tunnel projects ever undertaken in the UAE.

Linear heat detection

Patol has two systems which are widely employed in tunnel applications.

The first is Linear Heat Detection Cable (LHDC), an award-winning product designed to detect fire and overheating in circumstances where other forms of detection would not be viable, either due to an inability to sustain the environment requirements or through prohibitive costs.

It is particularly suited to use in road or rail tunnels where harsh environmental conditions can prove difficult for other forms of detection.

Tunnels are also typically characterised by increased air flow which can lead to false alarms in conventional smoke detectors, as well as inaccurate identification of the location of a fire. The Patol LHDC combined with the associated controller can provide accurate distance location to within one metre.

As a low maintenance system, LHDC is useful in areas that have restricted access for personnel due to physical obstacles or the risk to health and safety – drainage collection points, cable service tunnels and inlets are typical examples, all of which are potential installation locations for LHDC, as well as on the ceiling of the tunnel itself.

The LHDC controller with distance locator display can be configured to operate in two wire mode that emulates the operation of conventional heat detectors. This allows it to be interfaced directly with fire control panels or as part of an addressable loop.

Thermal imaging

The second option available from Patol for use in tunnel applications is FireTIR thermal imaging heat detection.

In the past, thermal imaging was seen primarily as a specialty technology.

Now, systems based on infrared camera technology are increasingly enhancing fire and security measures across many transportation projects, improving protection all over the world.

A major benefit of thermal cameras is that they enable timely detection and therefore intervention in important events.

High risk areas like bridges and tunnels can be constantly monitored for fires.

Early fire detection systems using infrared cameras can measure the temperature of any object in its field of view, allowing detection of fire at an early stage, long before traditional fire detection systems.

When it comes to roadway monitoring, thermal cameras are not adversely affected by glare from car headlights.

As such, they allow staff to clearly see vehicles, analyse traffic patterns and assess the cause of traffic disruptions, thereby reducing congestion and potentially speeding the dispatch of roadside assistance or maintenance crews.

By supplementing an existing maintenance programme with the use of thermal imaging, rail network operators can extend the operational life of their infrastructure, reduce the operational lifecycle costs of their assets and offer full visibility and situational awareness of any disturbances in depots, on the tracks, and around critical railway infrastructure.

Tunnels are a vital element of the transport infrastructure of any country.

Their construction represents a significant investment in terms of time and money, while their successful operation, timely maintenance and safety are crucial to a region’s economy.

This means that protecting them from the threat of fire with solutions designed to meet their specific challenges remains a key consideration.

This exclusive article was originally published in the June 2023 issue of International Fire & Safety Journal. To read your FREE digital copy, click here.