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Ionization Smoke Detector
- Teardown and a little reverse engineering -



     I took apart an old ionization-type smoke detector, made by Family Gard, Inc in December 1992. Other markings on the unit are: Model 835R, B60-151-74, B9147, QQJ89147, I87-35-04.

     This smoke detector was designed for residential use. I wanted to see how the smoke detector was wired and also to remove the piezo siren from it. Very loud piezo buzzers such as used in smoke detectors are not always easy or cheap to find, yet can be a lot of fun when added to random electronics projects. However, be warned that the re-use of these sirens is guaranteed to make you more annoying!

     Being an ionization smoke detector, this unit contains about 150 mg of americium 241, a radioactive substance. Luckily, americium emits only alpha radiation, and thus is mostly benign in this small of a quantity. Theorhetically, any alpha radiation emitted from ionization smoke detectors is harmless to humans unless you are doing something really stupid.

    For example, having the radioactive material in direct contact with your body for any length of time is a terrible idea. Likewise, sleeping on top of the smoke detector or with it in close proximity to you is also a bad idea. Don't do it! Also worth noting is that photoelectric (optical) and air-sampling smoke detectors exist which do not contain radioactive material. Most modern residential smoke detectors are the optical type.


Ionization Smoke Detector Photos

Photo Gallery Smoke Detector
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Photo Gallery Smoke Detector
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Photo Gallery Smoke Detector
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Photo Gallery Smoke Detector
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Photo Gallery Smoke Detector
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Photo Gallery Smoke Detector
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Photo Gallery Smoke Detector
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Photo Gallery Smoke Detector
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Photo Gallery Smoke Detector
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Photo Gallery Smoke Detector
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