Smoke detection – scattered light

Smoke detection allows a reliable and early detection of tunnel fires. An early detection is essential to maximise time for self-rescue.

Air in the tunnel flows through the sensor’s measuring chamber. The sensor then detects the intensity of light scattered by this sample. Thereby emerging fires can be detected at an early stage (cold smoke) long before fire alarm cables can detect the event. Individual thresholds can be set to trigger alarms or respectively the measured values can be used to do such in the tunnel control system.

Any influence caused by fog will be compensated by optional heating elements. The measurement is not affected by extraneous light, reflexes or other influences as is the case for video detection. Individual setting of parameters allows an optimal object and location related setting of alarms:

  • More time for self-rescue
  • No false alarms
  • Reduction of a possible damage to the object and of subsequent costs

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t/SMD Smoke detector

  • Mounting on wall, ceiling, false ceiling or integration in ventilation damper
  • Air supply through air flow in the tunnel
  • Visibility metering by scattered light
  • Optional heater to compensate fog
  • Connections boxes to connect to the tunnel control system either by
    • 4-20 mA / 2 relays
    • Profibus DP
  • Optional hand-held operating unit
  • Delivered ready for operation
  • Sensor to be mounted directly in the tunnel’s driving area (power supply by system cable from connection box)
  • Connection to tunnel control system through connection box (MODBUS RTU, Profibus DP, 4-20 mA and relays)
  • Optional hand-held touch operating unit
  • Rapid, reliable smoke detection without false alarms
  • Compact design, no moving parts
  • Fog compensation by optional heating elements
  • LED light source, very low power consumption
  • Permanent instrument monitoring in the background
  • Simple recalibration with recalibration plug
  • Flexible system integration
  • Simple recalibration with checking rod
  • No consumables
  • Extremely low maintenance costs
Technical Specifications
Smoke detection
Measuring method 120° forward light scattering
Measuring range 0 .. 3 m-1
Resolution 0.001 m-1
Response time 5 s (at an air speed of 1.5 m/s)
Type FireGuard 2
Power supply 24 VDC
Power consumption 4 W
Heater (optional) 13 W
Housing material Polycarbonate / stainless steel 1.4571
Protection class IP 66 (only electronics)
Dimensions Ø 107 × 283 mm
Weight 0.9 kg
Connection box
Power supply 85 .. 264 V / 47 .. 63 Hz
Power consumption max. 25 W
Housing material Polyester (glass fibre reinforced)
Protection class IP 66
Dimensions 220 x 120 x 95 mm
Weight 1.3 kg
Output modules • Profibus DP or
• 2 x 0/4-20 mA, 2 configurable relays
Operating unit with display
Power supply 24 VDC (via system cable from SIPORT 2)
Display Graphic TFT with touch operation
Housing material Plastic (ABS)
Protection class IP 65
Dimensions 130 × 160 × 60 mm
Weight 0.6 kg
Electrical standards 2006/95/EC Low voltage directive (LVD)
2004/108/EC Electromagnetic compatibility (EMC)


Product info DE (PDF, 353 kB)
Product info EN (PDF, 353 kB)