Tunnel monitoring - Environmental

Car tunnels need ventilation in order to keep air pollution below the limits. When the pollution levels reaches a setpoint, the fans must be started and kept running until the pollution levels decreases.

In many tunnels, the level of NO2 is the parameter that controls the ventilation. NO2 is the pollution parameter that first will exceed the air quality standards. To monitor NO2 inside a car tunnel is a challenge due to the difficult environment and need of accurate results around the setpoint. The same system can also be used for monitoring emissions in the ventilation stack.

OPSIS DOAS system provides an accurate analyser that will operate with a minimum of maintenance. Besides the measurement of NO2, additional gases such as NO, benzene and formaldehyde can be measured.


  • True monitoring of NO2 with high accuracy
  • Operates with a minimum of maintenance
  • Cost-effective, open-path technology
  • Gas calibration only once a year
  • Low energy consumption
  • Internationally approved
  • Thousands of systems installed worldwide
  • Serviced by highly skilled service network

System Overview