> Both decay through alpha-particle emission That decay also emits a gamma ray as a byproduct. The energy given off by these gamma rays is actually significan

> Both decay through alpha-particle emission That decay also emits a gamma ray as a byproduct. The energy given off by these gamma rays is actually significant at 59.5 keV. For example, let's assume you have $1500 in americium-241 in your mattress. At $1500/gram, that's one gram. With a specific activity of 3.43 Ci/g, that gram has about 3.66×10^15 decays in a 8 hour night. At 59.5 keV per decay the total gamma ray energy is about 35 J, or 500 mSv for a 70kg person. That's equal to 25 full body CT scans, or the yearly occupational dose limit, every night. Smoke detectors typically contain about a microgram of americium-241, so that translates to a nightly dose of 0.5 μSv, or a yearly dose of 550 μSv. That's about a quarter of the natural background dose. It's also the amount of radiation emitted by the smoke detector, not what you receive. At an average distance of 8 meters, you'll receive just 1/100th of that.