How Do Smoke Alarms Detect Smoke?
Ionization Smoke Detectors The most common type of smoke detector is the ionization model, which uses a tiny ionization chamber to detect the presence of smoke. The ionization chamber is flanked on opposite ends with metal conductors through which a live electrical current flows, powered either by 120 volt home wiring or a battery. The chamber also contains a trace amount of a radioactive substance called americium-241. This substance sheds radioactive alpha particles that ionize the oxygen and nitrogen atoms present inside the chamber. When ionization occurs, free electrons are cut loose from their oxygen and nitrogen atoms and receive negative charges. The negative free electrons become attracted to the positive conductor in the chamber, while the other positively charged particles get attracted to the negative conductor. This clears the inside of the chamber and strengthens the electrical current between the conductors. As smoke seeps into the ionization chamber through vents, the s
