Robert Gawron writes:
Not many people know, but in some smoke detectors, radioactive materials play an essential role. Today I will present one of those devices, and my -successful- attempt to reverse engineer it and get the circuit diagram.
Those smoke detectors uses a small amount of Americium-241 (chemical symbol: Am) obtained in nuclear reactors as a decay product of Plutonium-241. Am241 emits mainly alpha particles, but also some gamma rays. In smoke detectors it is in a form of an oxide Am02.
More details at Robert Gawron’s blog.