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Smoke Detector

Smoke Detector. Bret Spencer ECE 5320 - Mechatronics. http://www.familyhomesecurity.com/images/Smoke-Detector.jpg. Agenda. History Types of smoke sensors Problems Applications Further research opportunities. Why are they necessary?.

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Smoke Detector

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  1. Smoke Detector Bret Spencer ECE 5320 - Mechatronics http://www.familyhomesecurity.com/images/Smoke-Detector.jpg

  2. Agenda • History • Types of smoke sensors • Problems • Applications • Further research opportunities

  3. Why are they necessary? • Death rate in homes are 45% lower when a working smoke detector is present • Early and accurate detection of fires is crucial to minimize damage and loss of life Image courtesy of Wikimedia Commons

  4. History • First automatic electric fire alarm invented by Francis Robbins Upton in 1890 • Walter Jaeger’s failed poison gas detector functioned as a smoke detector in the late 1930’s • First commercial smoke detectors appeared in 1969

  5. Types of Smoke Sensors • Optical • Ionization • Aspirating • CO and CO₂ Detectors

  6. Optical • Uses LED and photodetector to detect presence of particulate matter • Two types • Scattered light • Blocked light

  7. Scattered Light Method • Under normal operation, the light passes the photodetector • Smoke scatters the light • Photodetector catches scattered light http://www.smokealarmdetectors.com/images/photoelectric%20smoke%20detector.jpg

  8. Blocked Light Method • A tight beam of light shines from source to detector • Smoke blocks path, triggering alarm • This type can span large rooms http://www.sas.org/tcs/weeklyIssues/2004-07-16/feature1/index.html

  9. Pros • Less Prone to false alarms • Less sensitive to steam and cooking fumes • Better at detecting smoke from smoldering fires

  10. Cons • Slower to detect smoke than ionization method LED Photodetector Image courtesy of Wikimedia Commons

  11. Ionization • A radioactive source ionizes the air between two electrodes • Changes in the current, due to particulate matter, trigger an alarm http://www.smokealarmdetectors.com/images/ionization%20smoke%20detector.jpg

  12. Pros • Detects particles too small to be visible • Cheaper than optical detector • Better at detecting smoke from hot fires

  13. Cons • Most prone to false alarms Ionization Chamber Image courtesy of Wikimedia Commons

  14. Aspirating • Air is drawn from different sampling points • Detector uses a solid-state laser and receiver to detect small particles Diagram courtesy of Wikimedia Commons

  15. Pros • Detects smoke very quickly • High sensitivity • Can detect multiple levels to smoke concentration • Wide coverage area

  16. Cons • Usually requires a large infrastructure • High cost Image courtesy of Wikimedia Commons

  17. CO & CO₂ Detection • Trigger an alarm based on toxic levels of CO or CO₂ concentration • Not a common type of fire detection

  18. Video Smoke Detection • Used in the Sydney Harbor Tunnel to successfully detect dangerous levels of smoke • Uses standard CCTV cameras that are already present for traffic purposes • Software detects evidence of smoke • Multiple cameras are cross-checked to minimize error

  19. Video Smoke Detection • Very fast detection • Image can be verified by operator • Very accurate sensing http://www.sourcesecurity.com/images/moreimages/IndustryNews/D-tec_Sydney_test_250.jpg

  20. Smoke Obscuration Levels

  21. Problems • Many residential smoke detectors do not function properly due to expired batteries • Kitchen smoke can cause false alarms http://www.cranleigh-fire-station.co.uk/smoke%20detector.jpg.jpg

  22. Applications • Smoke detectors are cheap enough to be placed in every room in any building • Central systems allow multiple sensors to sound multiple alarms Image courtesy of Wikimedia Commons

  23. Further Research Opportunities • Types of photodetectors and the effectiveness of detecting smoke of each • Electric CO and CO₂ detectors • Size of particulate matter and its effect on ionization and optic methods of detection

  24. Don’t let this happen to you! • Install smoke detectors • Test them regularly • Replace expired batteries https://www.myedgesoftware.com/images/burnt-house-trash.jpg

  25. Sources • http://www.smokealarmdetectors.com/how-smoke-detector-works.html • http://www.familyhomesecurity.com/how-to-choose-a-smoke-detector-for-your-home/ • http://home.howstuffworks.com/home-improvement/household-safety/fire/smoke.htm • http://www.sourcesecurity.com/news/articles/co-58-ga-co-2248-ga.2115.html

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