Smoke detectors commonly use the radioactive element Americium-241. This isotope emits alpha particles, which are then used in the ionization process to detect smoke. When smoke enters the detection chamber, it disrupts the flow of ions between two electrodes, triggering the alarm. Americium-241 has a half-life of 432 years, making it suitable for long-term use in smoke detectors. Although the levels of radiation in smoke detectors are low and deemed safe, proper disposal is necessary due to its radioactive nature.