Ionization smoke alarms are smoke alarms which create a conductive chamber with the use of radioactive materials. The conductivity of the chamber will fluctuate when particulates such as those associated with smoke enter the air; if the smoke alarm detects a particulate level which may be dangerous, it triggers a siren to alert occupants of a structure to the danger. Many hardware supply stores sell ionization smoke alarms, and fire safety groups sometimes give them out for free as a service to public safety.
These smoke alarms are especially well suited to fires which generate low levels of smoke, such as sudden, blazing fires. In addition to being sold as standalone units, ionization smoke alarms are also included in dual sensor smoke alarms, which are designed to detect several different types of fires. All smoke detectors should be regularly inspected and tested to ensure that they work, and the batteries should be changed on a regular basis as well. One of the best times to do this is during the time change, if you live in a region where the time changes, as you may already have to adjust various household equipment.
The innards of an ionization smoke alarm include a small chamber which is ionized with the use of a weakly radioactive substance. A current is passed through the chamber, with a sensor which is designed to detect subtle changes in that current. When smoke enters the ionizing chamber, it binds to the free ions, disrupting the current and triggering an alarm.
Ionization smoke alarms are not dangerous, but they should be handled carefully because of the radioactive material. Most of these alarms have a separate battery chamber so that you can change the batteries without handling the insides of the alarm; if the batteries are not in a separate chamber, open ionization smoke alarms carefully and avoid handling the ionized chamber directly. If you need to dispose of an ionization smoke alarm, use a qualified hazardous materials disposal service.
Smoke alarms are great fire safety tools, using very sensitive sensors to quickly alert people to danger. You should make sure that smoke alarms are installed on every floor of a structure, and ideally in every bedroom as well, to ensure that sleepers will be woken in the event of a fire. It is also an excellent idea to have fire extinguishers available for small fires, and to set up a clear fire evacuation plan with the occupants of a structure to ensure that everyone gets out safely in a fire.