Linear Heat Detection for Road and Rail Tunnels


A tunnel is an underground or underwater passageway that is dug through the surrounding soil, earth or rock. Except for usually an entrance and an exit at either end, tunnels are completely enclosed. Tunnels are used for a number of different purposes, however, one of their most common uses is to provide a passageway for foot or vehicular road traffic and/or rail traffic.

Due to tunnels being enclosed spaces with limited or restricted escape options twenty percent of people avoid using them if there is an alternative route available. It is for this reason that road and rail services continually advertise that their tunnels are protected by the most up-to-date, reliable and secure fire alarm systems.

There are huge fire risks associated with tunnels and the consequences of fire not only affect human life but also disruption to road and rail networks and delays in travel and supply chains.

Dartford Tunnel Fire

At the beginning of July 2016, a fire broke out in dartford tunnel causing drivers and passengers to abandon their vehicles. After a car caught alight in the middle of the tunnel travellers were forced to evacuate the tunnel while emergency services tackled the blaze.

Fortunately the fire detection system and suppression systems that were in place were able to detect and control the fire, stopping it from spreading to other vehicles and allowing everyone to escape unharmed.

Although no-one was hurt the tunnels remained closed for over an hour before they were cleared and made safe by the fire department.This closure led to significant delays for commuters, holiday makers and even emergency service vehicles.

What are the risks?

There are a number of fire risks associated with tunnels. Often with thousands of vehicles passing through each day, they are subject to high amounts of exhaust and other combustible gases not only increasing risk of fire, but also putting people that are trapped at risk of carbon monoxide poisoning. Malfunctioning vehicles also pose a high risk of fire.

In rail tunnels there are a also number of risks to contend with. Rubbish, food containers discarded cigarette ends left by passengers are all combustible materials at risk of ignition from arcing caused by trolling stock. Rail tunnels also often contain a number of lifts and escalator that are put under tremendous load each day, which could easily lead to mechanical or electrical breakdown and, ultimately, fire.

In both circumstances electrical cables used to power lighting and ventilation systems are at risk of overheating due to overloading or insulation breakdown.

What are the challenges?

Tunnels are often long, with limited access. They are often multi level constructions with a tangle of complex passages and shafts. Escape routes are greatly restricted and they usually contain a large number of people within concentrated areas.

What is the Solution?

FyreLine linear heat detection can provide the ideal solution for protecting tunnels from fire. Its ability to detect fire or excess heat from anywhere along its length means that fires can be located quickly and accurately in even the most complex of environments. FyreLine Linear Heat Detection Systems can easily be installed as part of an existing fire alarm system.

There are two versions of FyreLine linear heat detection systems available – FyreLine Digital, and FyreLine Analogue.

FyreLine Digital Linear Heat Detection System

FyreLine Digital heat sensing cable is made of two metal conductors that are coated in a heat sensitive polymer. These two conductors are twisted together and encased in an outer sheath. When the heat sensitive polymers reach their rated temperature they melt, causing the conductors to come into contact with each other. The resulting short sends a signal of fire to the fire alarm control panel.

View the FyreLine Digital brochure.


FyreLine Analogue Linear Heat Detection System

FyreLine Analogue heat sensing cable is of a similar construction. However, it also includes an ambient temperature sensing cable and a calibration cable, thus allowing the heat sensing cable to automatically compensate for changes in ambient temperature. As the temperature rises the resistance of the heat sensing cables changes, sending a signal of fire to the control panel. A pre-alarm temperature can also be defined to allow investigation before entering full alarm.

View the FyreLine Analogue brochure.

Typical Installation

FyreLine Linear heat sensing cable is typically installed along walkways, in ceiling voids, along cable trays and in moving platforms and escalators. It can also be installed under platform edges and in ventilation ducts to ensure maximum protection at all points.

For more information about the FyreLine Linear Heat Detection Systems, or to discuss any of the other products that Eurofyre have to offer, please feel free to get in touch either by phone on +44 (0) 1329 835 024, by email to [email protected] or via the online enquiry form situated on our contact page.

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