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smoke alarms dangerous?

Discussion in 'Beginner Electronics' started by steve marchant, Sep 5, 2005.

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  1. my son has taken apart an old smoke alarm cos he wants the sounder out of it
    for a project. I notice the detector element has "radioactive" engraved on
    its cover. He's taken the element apsrt and I'm wondering is this dangerous
    to handle, or even be near?


    Your smoke detector contains a small amount of Americium. It is not
  3. Phew! Thanks. I was quite worried.
  4. Alexander

    Alexander Guest

    Don't worry about radiation, until you start getting green, giving light or
    start growing out of proportion ;)
  5. Guest

    The detector contains a low power radioactive alpha emitter. It is safe
    when inside the ali housing, as alphas dont penetrate much. The housing
    absorbs them all. But when its removed the body will absorb the alphas
    when close or touching. How safe that is depends on the level of
    emissions. Of all radioactive particles, alphas are the most absorbed
    (100%) and thus cause more damage per particle than betas and gammas.
    OTOH the output will be very low.

    If he wants to play with it it ideally ought to be in a housing such
    that the direct emission path from souce to body is blocked. Sheet
    aluminium is enough to do this, no lead needed. The universe showers us
    with radioactive gamma particles continuously at a low level, so
    exposure to a few alphas are nothing to freak about.

    The other plus with a housing is it prevents it being eaten, which
    would be dangerous.

    Balance all this against the positive effects of the source:
    1. he can learn lots, develop interest, and maybe end up in a good job.
    2. he can see in the dark when hes glowing green



    Even swallowing the radioactive material from a smoke detector would not
    lead to significant internal absorption of Am-241, since the dioxide is
    insoluble. It will pass through the digestive tract, without delivering a
    significant radiation dose. (Americium-241 is however a potentially
    dangerous isotope if it is taken into the body in soluble form. It decays by
    both alpha activity and gamma emissions and it would concentrate in the
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