Bouygues Travaux Publics

Air quality monitoring in a tunnel


Boring of a tunnel in the T3A section of Grand Paris Express metro between the Pont de Sèvres and Issy-Vanves-Clamart stations.


Air sensors had already been installed when works began about 2 years ago.

The cline (Horizon – T3A joint venture) wanted to add CO2 level monitoring as legal limits had evolved on 1st July 2020.

Client can monitor the efficiency of ventilation in the tunnel so as to limit how much workers are exposed to specific gas in the tunnel.


Need: track CO2 levels.

Com’in solutions

Installation and connection to NuisAlgo platform beginning October 2020 until 2024 – 2025 when works are forecast to end. 8 hour and 15 minute average exposure limits have been set as alert thresholds on the platform.
Worksite receives alerts when these thresholds are exceeded.

Our sensors also record levels of BTX (benzene, toluene, xylene) thanks to the PID sensor. A suspicion of one of these compounds must then be confirmed by chemical-reacting tubes.

Levels of various gases, dust and VOCs are monitored as the tunnel is bored and we are optimising recordings as works progress.

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