replcing smoke heads

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fmtjfw

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The vast majority of residential smoke detectors are ionization type detectors. As the Americium loses activity, the current in the detector drops. Since it is the reduction of current caused by smoke particles attaching themselves to the ions in the ionization chamber that causes an alarm condition, eventually the detector will be constantly in alarm. Every ten years is the required replacement by NFPA 72, or sooner if the manufacturer calls for it.

It is more likely the electronics, the ionization detector or dust bunnies. Americium's main half-life is 141 years. The isotope used in smoke detectors has a half-life of 432.2 years. It is an Alpha emitter, which means "don't eat or breathe it".
 
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