TunnelMaster NO₂ Sensor

 Nitrogen dioxide (NO₂) is fast becoming the most important measurement in tunnels and will eventually replace NO as the key measurement. The TunnelMaster NO₂ Air Quality Monitor (AQM) uses both infrared and ultra-violet light channels to detect the smallest concentration of gas in a single compact instrument.

   The AQM consists of a transceiver that projects infrared and ultra-violet light beams to a reflector within a stainless steel tube mounted 1m away. Sintered filters in the measurement chamber allow gases from the tunnel atmosphere to diffuse into the chamber while inhibiting the passage of particulates.