Ventilation and Noise Control Resources

Tunnel Dampers: The Basics

Posted by Richard Yarges on Mar 8, 2017 1:45:17 PM

Commuters do not often think of disaster scenarios when they travel through transportation tunnels, but the engineers behind the scenes are acutely aware of just what can go wrong when the proper safety precautions aren’t in place. Whether it’s a tunnel for vehicular traffic, subways, or a train, tunnel dampers are essential for maintaining life safety in the event of an emergency.

The main concern for disaster preparedness is a fire. Unfortunately, we have seen such disasters take place around the globe, but the industry has learned from those tragic events. There are now worldwide regulations in place to avoid future incidents such as NFPA 130, NFPA 502, and BS476-20.

An essential component to a safe transportation tunnel is the dampers. As with any fire, when a fire erupts in a tunnel, the greatest concern is the smoke. Essentially, the dampers allow you to isolate certain sections of a tunnel so people can escape from a fire without being overtaken by smoke.TUNNEL 2.jpg

How do fire dampers work?

The dampers are connected to fire detectors (heat, smoke, etc.) so the safety systems are triggered automatically. It is usually connected to a control room where there are crews observing and ready to act in the event that the automated system fails. When the detection system is triggered, the dampers adjacent to the area where there’s a fire are opened while the other dampers are closed. In this way, the smoke is extracted near the fire and it allows people in the tunnel to evacuate without much exposure to the smoke. In many cases, reversible flow fans are installed to help pull the smoke out of the tunnel as well. 

Tunnel Damper Certification Standards

For train tunnels in the United States, dampers need to withstand 482°F for an hour and able to withstand 21 pressure reversals per hour. Vehicular transportation tunnels have the same temperature requirement, but may have reduced requirements for pressure. For customers in other parts of the world such as Europe and East Asia, requirements may be more stringent with dampers remaining operable for 120 minutes at 400°C.

Maintenance Issues

A key component you should consider when purchasing tunnel dampers is the maintenance. Do you have the appropriate staff to perform maintenance? We always suggest scheduling routine preventative maintenance to ensure that the dampers are cycled every so often. To say it would be disappointing would be an understatement if you find out one of the actuators has failed during an emergency.


Tunnel dampers provide a high standard for life safety ventilation in the transit systems. They provide normal ventilation and smoke control during emergency situations. Eldridge can provide the right Flamgard damper for your next tunnel project. Give us a call today.

Free Ventilation Tips

Trusted Solutions. Reliable Engineering.

By signing up for our AirMail Newsletter, you'll receive the latest ventilation and noise control resources directly in your inbox. AirMail is only sent out once a month, so we won't overload your inbox!

Besides great resources and tips, you'll get:

  • Latest news
  • Classic AirMail
  • Info on new applications and products
airmail-logo

Subscribe to AirMail!