TECHNICAL | SAFETY/FIRE


A) Distributed exhaust


Right, figure 2:


(from top to bottom): Smoke control with 150m3


different ventilation concepts


Figure 2a:


Distributed exhaust Figure 2b:


Local exhaust with smoke dampers


Figure 2c:


Local exhaust with smoke dampers and control of longitudinal flow


Airflow [m/s] C) Local exhaust with smoke dampers and control of longitudinal flow Length [m] /s exhaust for three


Airflow [m/s] B) Local exhaust with smoke dampers


Length [m]


Airflow [m/s]


Length [m]


After the fires, smoke tests were performed in


other tunnels. The observations quickly lead to upgrades of the ventilation systems and to the installation of smoke dampers. At the time, there was no market for this equipment. Smoke dampers had to be designed, constructed, and tested specifically for the application. Different damper types were tested in the San Bernardino Tunnel in Switzerland.2


Dampers with


sliding blades and linear actuators, single-blade dampers using a movable counterweight, and, the parallel-blade dampers that we use today, as shown in Figures 1, 3 and 4. The change from distributed to local smoke extraction


was so swift that, in 2007, a World Road Association (PIARC) report2


states: “Extraction capacity is usually concentrated to a zone smaller than the length of the 12 | August 2023


duct by addition of motorized, remotely controlled dampers.” The report lists several tunnels that had then been recently equipped with smoke dampers. In the 2011 PIARC report3


on emergency ventilation


operation, it is mentioned that “Recent developments of transverse systems incorporate remotely controlled dampers enabling point smoke extraction.” In 2011, the traditional system of distributed smoke extraction has all but disappeared from design considerations for new tunnels.


EFFECTIVE? To understand the differences between distributed and local exhaust, three simulation scenarios were performed using a 1-D software model4


spread of smoke from a fire incident in a tunnel.


to study the


Time [min]


Time [min]


Time [min]


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