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A tunnel is essentially a passage created through surrounding soil or water, totally enclosed except for the entrance and exit. With the increase in vehicular traffic, urban planning is increasingly using tunnels for traffic movement since they reduce travel time, and clear surface vehicles from long distance roads. Due to the nature of tunnels being entirely enclosed for the length of the distance, air pollution within can become highly concentrated. Gases like carbon dioxide, nitric oxide and nitrogen dioxide released from vehicular traffic, and fine particulate matter can cause health hazards ranging from respiratory problems to heart issues. Fine particles, when gathered in dense concentrations, can also reduce visibility considerably presenting a significant driving hazard.

Ventilation in tunnels is a therefore critical need for safety and comfort of users. It ensures proper air quality and control, reduces air temperature and controls smoke in the event of a fire. However, costs of operating a tunnel ventilation system can be quite high. A reliable tunnel atmosphere monitoring system continuously measures concentration of gases in the tunnel and monitors visibility, triggering the ventilation systems into action only when needed to clear pollution.

Tunnel monitoring systems help monitor critical parameters like

- Air flow

- Carbon monoxide

- Nitric oxide

- Nitrogen dioxide

- Visibility

- Smoke

- Wind speed and wind direction

- Light intensity


Various technologies available for tunnel monitoring include infrared, ultrasonic, luminance, illuminance and electrochemical cell technology.

Codel International, a Forbes Marshall company based in the UK, offers a wide range of tunnel monitoring solutions. Available as stand-alone sensors or integrated into a network system, these sensors are installed in over 350 road and rail tunnels worldwide. Read more about our solutions here . The chart below gives an overview.

tunnel monitoring systems