VIPA Visibility Stand Alone Monitor for Tunnels

VIPA provides a dependable solution to the requirement for stand alone visibility monitoring in the tunnel environment.  The instrument consists of a transmitter head  and receiver head mounted 6m apart on the tunnel wall or ceiling.


The VIPA tunnel monitor makes a visible opacity measurement to determine  the visibility within the tunnel. These measurements can be used as  part of an air quality management system for ventilation control and/or  secondary smoke detection within a traffic tunnel, rail tunnel or other  confined space.

The VIPA sensors, consisting of a Transmitter (TX) and Receiver (RX), are mounted “facing” each other on the wall or ceiling along the length of the tunnel. The VIPA uses a single pass light transmission technique to measure dust, smoke and particulate concentration present in the atmosphere. The TX emits a visible (green) optical beam which is received by the RX.

Any dust or smoke particles present will attenuate the light beam and cause the intensity of the light received by the RX to fall. This reduction in light intensity is used to determine visibility in the tunnel.


  • Visibility measurement using the universally accepted single pass light transmission opacity technique
  • User selected unit display options of Opacity (%), Extinction Coefficient (k) or Meteorological optical Range (MOR)
  • Choice of interface options enabling easy integration into tunnel control system
  • IP65 / NEMA 4X rated external enclosure supplied with quick release dust protection tubes and wall brackets
  • Supplied complete with PC based utility software for set-up and control of the instrument


  • Designed specifically for monitoring in tunnels
  • Rugged design to withstand corrosive atmosphere and regular tunnel washing
  • Simple installation and alignment
  • No moving parts and low maintenance requirements
  • Right or left hanging option to enable compliance with regulations governing tunnel light emissions facing on-coming traffic flow
  • Flexible integration options

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