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Smoke Detectors

Smoke Detectors. Jr. Lab II, sp’01. Brief history

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Smoke Detectors

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  1. Smoke Detectors Jr. Lab II, sp’01 • Brief history • 1930s, Swiss scientist Walter Jaeger tried to invent poison gas detector thinking the particles would interact with an ion gas causing a detectable change in current. The idea failed. Frustrated, he lit a cigarette and voila, smoke detector. [1]

  2. Two Types • Photoelectric • Smoke particles encounter light beam • Beam scatters to a photocell creating a current • Better for larger particles (smoldering) • Ionization • Particles attach to ionized particles creating a detectable change in current • Better for smaller particles (flaming)

  3. Ionization Smoke Meters

  4. Ionization Source • Americium-241,243? • Emits  particle which ionizes the air molecules [2]

  5. References • [1] Bunker, Merton Jr., Scientific American, “Smoke Detectors,” Apr. 1997. www.scientificamerican.com/0497issue/0497working.html • [2] www.webelements.com • chemistry.about.com/science/chemistry/library/weekly/aa020700a.htm • Geoffrey, www.madsci.org/posts/archives/feb98/888079238.Ph.r.html www.britannica.com/search?query=americium

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