Smoke detectors

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Smoke detectors

  1. 1. SMOKE DETECTORS
  2. 2. NDTV October 27, 2010 17:39 IST Gurgaon: A fire at Gurgaon's Ambience mall was extinguished this evening. Nobody was hurt. Two fire engines were sent to the mall after a fire was reported at the Osim showroom on the second floor of the mall. Smoke could be seen billowing from the second floor near the fire, but the mall was not evacuated.
  3. 3. • disk-shaped plastic enclosure about 150 millimetres (6 in) in diameter and 25 millimetres (1 in) thick • 1890 by Francis Robbins Upton • 1930s the Swiss physicist Walter Jaeger
  4. 4. Optical Sensor • light passes in front of the detector in a straight line • smoke enters the optical chamber, light is scattered by the smoke particles • Good in detecting smoke generated by smoldering (cool, smoky)
  5. 5. Optical Sensor 4 – Photodiode 5. - LED
  6. 6. Ionization • an ionization chamber -air-filled space between two electrodes • Small constant current between the electrodes • Smoke reduces the ionization and interrupts this current • Am Alpha emitter has a half life period of 432 years • quicker in detecting particulate (smoke) generated by flaming (hot) fires
  7. 7. Ionization Smoke Detector
  8. 8. Air Sampling Smoke Detector • work by actively drawing air through a network of small-bore pipes laid out above or below a ceiling • Air samples are drawn past a sensitive optical device, often a solid-state laser
  9. 9. Air Sampling Smoke Detector
  10. 10. Commercial Smoke Detectors • Conventional – Resemble an electric switch • Analog Adressable – Detectors have an address
  11. 11. Fire Alarms • Manually actuated devices – Break glass stations – Buttons – Manual Pull Station • Automatic devices
  12. 12. Fire Alarm Notifications • Audible • Text Visual • Olfactory Stimuli

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