|Power Supply||9 V|
|Mounting type||Roof and Wall|
Smoke alarms will detect most fires more rapidly than heat detectors. There are currently three types of smoke alarms on the market: ionization, photoelectric and combination ionization/photoelectric. An ionization smoke alarm contains a small amount of radioactive material. The radiation passes through an ionization chamber which is an air-filled space between two electrodes and permits a small, constant current between the electrodes. Any smoke that enters the chamber absorbs the alpha particles, which reduces the ionization and interrupts this current, setting off the alarm. This type of alarm responds best to fast raging fires. Photoelectric smoke alarms operate using a light source, a light beam collimating system and a photoelectric sensor. When smoke enters the optical chamber and crosses the path of the light beam, some light is scattered by the smoke particles, directing it at the sensor and thus activating the alarm. This type of alarm responds best to slow smoldering fires. Combination smoke alarms feature both ionization and photoelectric technologies. Ionization smoke alarms respond faster to high energy fires, whereas photoelectric detectors respond better to low energy smoldering fires. The NFPA recommendsusing both smoke alarms in the home for the best protection.