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The Swedish Ministry of Transport has applied RFID technology to air quality monitoring in the Norra Lönken tunnel, which is located in the north of Stockholm and is 6 kilometers (3.7 miles) long. It is currently under construction. Since February 2009, the RFID system has been put into use, and it is expected to be used by the completion of the tunnel project in 2015. The solution will be provided by Identec Solutions.
The North Loop Tunnel consists of five construction areas and is managed by five separate tunnel contractors. Each worker wears an RFID badge with a built-in gas sensor to monitor the air quality around the worker to ensure their life safety; RFID readers are installed in the tunnel to locate the worker’s location. According to the data collected by RFID, the speed of the exhaust fan in the tunnel is automatically adjusted.
Before the system is installed, it is necessary to manually start the exhaust fan regularly. The sources of air pollution in the tunnel are mainly exhaust from fuel equipment and automobile exhaust.
As part of the tunnel personnel safety monitoring system, IDENTEC SOLUTIONS has started to develop an automation solution called an automatic ventilation control system. The security monitoring system for tunnel personnel includes three parts: closed circuit monitoring (CCTV), access control and alarm. The automatic ventilation control system provides a new safety guarantee for the staff: real-time monitoring of air quality and automatic activation of exhaust fans.
The solution includes Identec’s SensorSmart active i-B2 CC tags, the same type of ultra-high frequency (UHF) tags used to identify vehicles in the tunnel. Now, about 1200-1500 i-B2CC type tags have been deployed.
Fixed readers with 70-80 ports are installed at the intersections and entrances of the tunnel. These readers run through the entire tunnel and divide the tunnel into different monitoring areas. The data transmission distance of the tag can be up to 100 meters (328 feet), and the unique codes of workers and vehicles are sent every two minutes. The sensor used in the system is produced by GFG, which mainly measures the content of nitrogen dioxide (NO2) and carbon monoxide (CO) in the tunnel, and forwards the measurement information to the SensorSmart software through a wired connection.
The SensorSmart software is installed on the central server of the Ministry of Transport. The code of each label is associated with the employee number and the contractor, and is stored in the SensorSmart software database. Analyzing the data obtained from the sensor, if the content of CO or NO2 in the tunnel exceeds the standard, the system will automatically increase the exhaust volume of the exhaust fan to accelerate the air flow in the tunnel. Of course, the automatic ventilation system will automatically stop the exhaust under special circumstances to prevent an explosion.
Frank, the general manager of IDENTEC SOLUTIONS, said: The software monitors the gas content in the tunnel and the speed of the exhaust fan in real time.
In addition, the personnel monitoring system can also track personnel and automatically turn on the tunnel monitor when an emergency occurs.
The automatic ventilation system also contributes to the energy saving of the project. When the RFID tag detects that there are workers in the tunnel, the exhaust fan is in working condition, otherwise the exhaust fan is turned off.
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