Sweden’s national transport administration, Trafikverket, is employing RFID tags to transmit air-quality data to trigger ventilation controls within the 6-kilometer-long (3.7-mile-long) Norra Länken (Northern Link) tunnel, currently under construction in northern Stockholm. The RFID system, provided byIdentec Solutions, has been in use since tunnel construction commenced in February 2009, and is slated to continue through 2015.
The tunnel consists of five construction areas, managed by five separate road and tunnel construction contracting companies. The technology allows the agency to monitor airflow throughout the tunnel, in order to ensure construction workers’ safety, by providing each employee with an RFID badge, and by installing gas sensors that measure the levels of toxic gases around each individual, as well installing RFID reader to help determine the locations of workers within the tunnel. That data can then be used to automatically adjust the output of six tunnel fans within the tunnel, intended to ventilate the underground area.
Air ventilation for tunnel construction crews typically consists of a non-automated use of fans to ensure that fresh air is flowing into the tunnel, and that any unhealthy air is removed. The air can be contaminated by the fuel-operating equipment and vehicles located within the tunnel.
Identec Solutions has begun offering its automated solution, known as the Automated Ventilation Control System, as part of its Watchertunnel personnel-safety technology portfolio. Trafikverket has been the company’s first customer. Watchertunnel, a broad solution for tunnel construction safety management, includes closed-circuit television (CCTV), access control and alarms. The Automated Ventilation Control System provides a new layer of security, the firm reports, by monitoring air quality and providing an automated fan response.
The solution consists of Identec’s SensorSmart badges that have battery-powered Identec i-B2 CC tags. The badges are worn by staff members, and the same type of ultrahigh-frequency (UHF) tag has been attached to numerous vehicles used within the tunnel. A total of 1,200 to 1,500 i-B2 CC tags have been deployed to date.
Between 70 and 80 fixed i-Port MB readers have been installed throughout the length of the tunnel at cross roads, entrances and passages, thereby dividing the tunnel into distinct zones. Each badge transmits at a distance of up to 100 meters (328 feet), to readers set up in zones within the tunnels. Each personnel badge and vehicle tag transmits a unique ID number, every two seconds. Sensors from GfG measure levels of nitrogen dioxide (NO2) and carbon monoxide (CO) in the tunnel and forward that data via a wired connection to the SensorSmart software. Carbon monoxide is an odorless, colorless gas that can be fatal at high concentrations. Nitrogen dioxide is corrosive, and exposure to high levels of the gas may result in pulmonary edema and lung injury, as well as contribute to the development of acute or chronic bronchitis.
The software is installed on a central server at Trafikverket. There, on the SensorSmart software, each tag or badge ID is linked to a particular employee or vehicle, as well as to the contractor with which that person or vehicle is affiliated. The sensor data is evaluated in order to determine if there is an excessive presence of NO2 or CO in the air around each individual. If the system determines that either gas is nearing a toxic level, it can turn on or speed up the ventilator fan within that vicinity. The automated ventilation system is also designed to allow management to shut off the fans in the event that blasting is underway, and to increase speed following an explosion.
The software displays real-time and historical information regarding gas levels and fan speed, says Frank Wehus, Identec Solutions’ general manager.
In addition, the Watchertunnel system enables management to track the specific zone in which each individual is located in the event of an emergency, and can trigger the use of CCTV footage (cameras are installed throughout the length of the tunnel). For example, Wehus says, if an alarm is sounded, “you can view CCTV stream and/or a CCTV clip,” to determine if someone has entered an unauthorized area.
The ventilation system can also be programmed to activate fans only if workers are present. For instance, if an RFID tag is detected within a specific section of the tunnel, the system would turn on the fan in the immediate area. If individuals were to leave the area, the fan could be shut off.