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  • Over 20 years experience
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  • Road and Railroad tunnel
  • Smoke exhaust solutions


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Traffic can reach up to 200 000 vehicles a day in a road tunnel and the safety of users is a major issue. A fire taking place in a tunnel can have awful consequences and the smoke propagation speed can sometimes reach 4m/second.


Context and issue

The risks of a fire in a confined space are: Asphyxia, loss of visibility, explosion, collapse and the rise in temperature.

Rise in temperature and radiation

In case of a light or heavy vehicle catching on fire, the heat emitted is extremely dangerous for men and safety distances must be observed to ensure the user’s survival.

Propagation of smoke

Smokes swiftly spear throughout the tunnel causing a loss of visibility and asphyxia.

Smoke exhaust processes

Depending on the tunnel’s typology different solutions are set up.

Longitudinal ventilation

It is designed to push the somkes towards the entrance of the tunnel by the mean of axial fans. There also exists variants of that strategy, using massive extraction dampers.

Transversal ventilation

In the event of fire, it is designed to renew the tunnel’s air by extracting the smoke through the ceiling and blowing fresh air through the bottom.

Equipments requirements

The many elements composing the ventilation system are subject to security standards testing their heat resistance.

Acoustic constraints


Context and problematic

Acoustic in tunnels must be taken care of in regards to both users and neighbors.

Road and railway tunnels

Road and railway tunnels are not always subject to acoustic measures. Silencers and acoustic walls can be applied in some situations.

Subway tunnel

Subway tunnels are located in urban areas and receive public. Acoustic measures inside are set  by the Engineering office and the neighbor’s noise regulation.

Material characteristics

Extensive studies must be led in order to set up the optimum solution so as to reach the acoustic objective.


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Safety in road tunnels:

2000-63 Directive

It describes the measures to be taken for sanitary ventilation and smoke exhaust in a tunnel. It recommends a heat resistance test for the smoke dampers, following an accurate protocol:

Time Position T°in the tunnel T° in the duct
15 min Opening 400°C 20°C
60 min Opening and closing 200°C 200°C
60 min Opening 400°C 200°C


The splitters and silencers are not specifically called in the directive, but since they are located close to the fans in transversal and semi transversal ventilation, it can be considered that they have to be 200°C for 2hours resistant, or 400°C for 2hours resistant if they are located close to the smoke exhaust dampers.


The CETU (Center of Tunnel Studies)

In 2003 they edited a ventilation file explaining the different strategies of transversal or longitudinal smoke exhaust processes. It also gives many specifications regarding the sizing of dampers or the calculation of the optimal air flow depending on the situation (sanitary or smoke exhaust ventilation)



Safety in train tunnels

Technical ministerial instruction n°98-300

It describes the measures to be taken for safety in road rails tunnels. A smoke exhaust strategy is mandatory in tunnels located in an urban area and dedicated to public transport as well as in tunnels over 5 000 m long where the transport of hazardous materials is allowed.



European and international regulations:


European Directive 2004/54/CE

It describes the measures to be taken regarding the cooperation between the different security centers of  a trans-European tunnel. It also explains the necessity of installing massive extraction dampers in bidirectional trans-European tunnels over 3 000 m long.



World Road association

The WRA is an organization that publishes and gathers different elements regarding fire safety in tunnel throughout the world, be it on heat regulation, pressure regulation or leakage rates. Its activity is close to the CETU’s and their files also contain data on sizing and calculation.



The 20th article of the British Standard applies to fire and smoke dampers. The protocol is composed of:

An integrity test  with a closed damper following the ISO 834 curve (curve T°/time)
An fire tightness test :  -     No flames shall go through the damper during the test

A rod of more than 6 mm in translation of more than 250 mm through the damper shall not go through it
A 21 mm rod shall not go through the center of the damper 



The UL555S (Underwritters Laboratories) specifically describes the necessary test on a smoke damper so that it can be used in the USA or in any other country that uses this regulation. Its requirements cover smoke dampers used in Heating, Ventilation and Air-Conditioning (HVAC). The tests are always operated on 3 dampers (max height/max width, min height/max width, max height/min width).

The tests on the smoke dampers bears on different criteria:

Operability: 100 000 operating cycles from opened to closed via all the intermediate positions of the blades.
Heat resistance : beginning at a temperature of 121C° with a rise of 56°C every 30minutes in closed position
The leakage rate is measured by applying heavy water pressure (from 1.1kPa to 3.1Pa) on the damper. It is then evaluated from class 1 to 3 depending on the results.


Acoustic regulation:

Neighboring noise, 2006-1099 directive, August, 31 2006

It describes the regulations that tunnel’s equipments are subject to when they are near an inhabited area. The maximum values for emerging sounds are 5dBA by day and 3dBA by night.



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