As mentioned above, the user has access to several devices for use in a tunnel, particularly in emergencies. These devices include fire extinguishers, emergency stations (containing emergency telephones and fire extinguishers) and emergency exit doors.
Automatic alarms are triggered when emergency systems such as doors and/or extinguishers are used. For fire extinguishers, it is the action of removing the equipment from its support that triggers the alarm. For emergency station and emergency exit doors, it is the opening of the door or the detection of a presence in the exit that is the trigger.
The opening of a door or removal of an extinguisher will often result in automated actions being triggered. For instance, a CCTV camera may be programmed to automatically turn to the door that was opened to aid a more efficient response by the operator. It is essential for the tunnel operator to be informed as early as possible when a user operates one of these devices, in order to take adequate actions. Where national standards require the tunnel to be monitored by full time Operators, then these devices will be monitored using switches. These switches are connected to the plant monitoring SCADA system. In the event that a door is opened, or an extinguisher removed, then the plant monitoring system will raise an alarm to the operator located in the control room.