UTILIZATION OF VISIBILITY MONITORING FOR FIRE DETECTION

BASICS OF VISIBILITY MONITORING Continuous measurement of visibility and CO-concentration has been used for ventilation control in road tunnels for almost 40 years

 Visibility is measured in units expressing the extinction of light over a certain distance, E/m (extinction per meter) or, more convenient, mE/m (milli- extinction per meter)  1 mE/m means the light intensity is reduced by a factor of 10 over a distance of 1000 meters BASICS OF VISIBILITY MONITORING: UNIT

BASICS OF VISIBILITY MONITORING: TYPICALLY MEASURED VALUES & LIMITS Normal Traffic< 5 mE/m Heavy Traffic ~ 5 mE/m Traffic Jam ~ 7 mE/m Closing of the tunnel 12 mE/m Fire > 15 mE/m

VISIBILITY MONITORING AND FIRE DETECTION: WHAT IS MEASURED? Visibility measures:  In normal operation: Soot from exhaust fumes, wear debris from the tires, dirt particles, etc.  In case of a fire: Soot particles and other products produced by the fire  Fog / Water steam (not desired!)

 Fire sensor cables measure the temperature and react either above approx. 50°C or at a certain temperature gradient. In case of a fire, these conditions are only achieved in an advanced stage.  Visibility monitoring also detects cold smoke, typically produced in an early stage, or in case of a smoldering fire  Advantage visibility monitoring: it enables earlier warning! VISIBILITY MONITORING AND FIRE DETECTION: COMPARISON WITH FIRE SENSOR CABLES

 The visibility values increase quite quickly over 15 mE/m, however, this information was not used for fire detection  In the worst case, more fresh air is pumped into the tunnel by the ventilation system, based on the assumption that the emission is too high  Consequences: the fire gets more oxygen and the smoke is distributed in the tunnel VISIBILITY MONITORING AND FIRE DETECTION: EXPERIENCE FROM FIRE INCIDENTS

SMOKE DETECTOR FIREGUARD  Measuring principle: stray light  No moving parts  Response time: T90 in 5 second  Integrated temperature sensor  Fog elimination with heating elements (option)  Signal output via relays or Profibus DP  Installation on the wall, ceiling or in the intermediate ceiling of the fresh air channel

FIREGUARD INSTALLATION: WALL MOUNTING

FIREGUARD INSTALLATION: MOUNTING ON THE CEILING

FIREGUARD INSTALLATION: MOUNTING IN THE INTERMEDIATE CEILING

CONSEQUESCES FOR THE VISIBILITY MONITOR: INSTALLATION POINT  Where is the most ideal place for the system installation?

CONSEQUENSES FOR VISIBILITY MONITORING: INSTALLATION POINT  Smoke is normally concentrated under the ceiling  In-situ instruments are normally already mounted about 3 meters above the ground  Suction points for extractive instruments should also be mounted at the same height (currently they‘re about 1.5 meters above the ground)

mE/m 17:08: :08:4517:09:0017:09:1517:09:3017:09:4517:10: Relais VisGuard FireGuard Wand FireGuard Decke 1 (3m) FireGuard Decke 3 (3m) FireGuard Decke 4 (3m) Geräte Vortunnel Relais: 3: normal 2: Voralarm 1: Alarm 0: Störung CONSEQUENSES FOR VISIBILITY MONITORING: INSTALLATION POINT

CONSEQUESCES FOR THE VISIBILITY MONITOR: ALARM LEVEL  What signal levels can be expected during normal operation and in case of an incident?

CONSEQUESCES FOR THE VISIBILITY MONITOR: ALARM LEVEL

Zoom: after approx. 30 to 60 seconds, depending on the distance of the visibility monitor from the fire, a limit of 30 mE/m has been exceeded. At the same time it could be demonstrated, that 30 to 50 m/Em is a realistic threshold for a smoke alarm

FIREGUARD: FIELD TEST GOTTHARD Zoom: The instruments FireGuard ceiling 1 und FireGuard prototype (wall) give an alarm more or less simultaneously; the instruments FireGuard ceiling 3 (200m distance) and 4 (300m) react with a delay of 22 and 58 seconds, respectively.

FIREGUARD: FIELD TEST NORWAY The Norwegian Road Authority conducted a fire test in Norway (Runehamar) to compare the reaction and sensitivity of fire detection systems based on optical cables and stray light. The test demonstrated that both system detect fire quickly and reliably. However, stray light instruments detected the start of the car fire 2 ½ minutes earlier (because there was only smoke in the beginning)

FIREGUARD: FIELD TEST NORWAY Direct fire (untypical) of 1 MW: Immediate response of the sensor cable, followed by the FireGuard. Note: a competitive unit made a self-test during the start of the fire and missed it!

FIREGUARD: FIELD TEST NORWAY Direct fire (untypical) of 0.1 MW: Sensor cable and FireGuard give alarm at about the same time. However, the alarm level for the sensor cable is based on very small temperature changes, hence there’s a higher risk of a false alarm!

FIREGUARD: FIELD TEST NORWAY Car fire (realistic incident): FireGuard triggered alarm after approx. 40 sec. The sensor cable only after more than 3 minutes! This is because in the beginning there was only smoke (in 90% this is the case!)

FIREGUARD: FIELD TEST NORWAY Car fire (realistic incident): This graph shows now the temperature signal. The sensor cable reacted just a little bit before the temperature sensor which is built in the FireGuard.

 Visibility monitoring is now used not only for the ventilation control, but also for early fire detection  It allows to detect smoke and smoldering fires in an early stage  Real fires are typically detected 2 to 3 minutes ahead of fire sensor cables  For the installation, new requirements concerning the instrument density and mounting place have to be considered  Alarm levels for fire detection must be defined individually for each tunnel. VISIBILITY MONITORING IN ROAD TUNNELS: SUMMARY