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TunnelTech 203

CO, NO Monitor

The TunnelTech 203 Air Quality Monitor continuously monitors CO, & NO and is an essential part of any road or rail tunnel safety system.


The TunnelTech 203 Air Quality Monitor is an essential part of any road or rail tunnel safety system. Firstly, it monitors the atmosphere within the tunnel and ensures that the tunnel ventilation system provides sufficient clean air to protect tunnel users health and for drivers to clearly see the road ahead.


The TunnelTech 203 analyser uses well proven infra-red techniques to determine CO and NO concentrations. 


As there is only one moving part, reliability levels are very high and maintenance requirements are extremely low.

Features & Benefits

Product Specification

Gas Species OptionsSingle or multi-gas measurements available: CO & NO
Measuring Unitsppm for CO, m-1 or m for visibility
Response TimeCO 2mins / Vis 10s – 2min Selectable
Ambient Temperature-20°C to +50°C
Power Supply12 – 24V dc 1.5A
ConstructionCorrosion resistant epoxy coated aluminum housing sealed to IP65
Analogue Outputs3 x 4-20mA current outputs as standard, isolated, 500Ω maximum load, fully configurable
through TunnelTech software.
Relay Outputs3 x volt-free SPCO contacts, 50V, 1A max, configurable as alarm contacts
Serial DataFor local connection to laptop PC using RS232 or optional RS485 interface unit

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