The TunnelTech 200 Air Quality Monitors continuously measure CO, NO, NO<sub>2</sub> and Visibility in road and rail Tunnel Monitoring applications.
For Tunnel Monitoring the TunnelTech 200 Series (201, 202 & 204) monitors the atmosphere within the tunnel to insure a tunnel ventilation system provides sufficient clean air to protect tunnel users health and for drivers to clearly see the road ahead.
The TunnelTech 200 (201, 202, & 203) Tunnel Monitoring Analyzers also use well proven infra-red techniques to determine CO and NO concentrations and optical attenuation to monitor Visibility levels. As there is only one moving part, reliability levels are very high and maintenance requirements are extremely low. The sight tubes have been designed to ensure that airborne dust and contaminants do not reach the optical windows and cause drift.
Fully configurable analog and alarm outputs are exportable to the tunnel data acquisition system to provide real-time CO, NO and Visibility data.
The TunnelTech 205 measures NO2 utilizing a very accurate measurement technique whereby UV and blue light are absorbed by NO2. The TunnelTech 205 is a precision transmissometer which measures the attenuation of UV and blue light by NO2 in the tunnel atmosphere. The light source is a near infrared LED where the interfering effects of particulate in the atmosphere are eliminated by making the measurement within a meter-long diffusion cell into which the atmospheric gases, but not the particulate, can freely diffuse.
The result is a very accurate and stable sensor having no moving components and requiring no maintenance throughout its lifetime. Even the optic surfaces remain clean because they are contained within the diffusion cell which prevents the deposition of dirt on them. The filters through which the gas diffuses do not become blocked because the diffusion process exerts no forces on particulate to force them into the filter pores.