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Know How Your Smoke Alarm Detects Fires
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 There are two types of smoke detectors, and it's important to know what you have, and what you may need.
Ionization smoke detectors are the most common, found in about 98% of homes. They are most responsive to flaming fires. They work by using radioactive material which ionizes the air and creates a current flowing between two electrically charged plates. Smoke entering the chamber disrupts the flow of ions and the current, thereby activating the alarm.
Photoelectric smoke detectors are generally more responsive to fires that begin with a long period of smoldering. These alarms aim a light into a sensing chamber at an angle away from a sensor. Smoke entering the chamber reflects light onto the sensor, thereby activating the alarm.
Neither one of the two types is "better," since each is more effective at detecting different type of fires.
So which to choose? Obviously you would never know what kind of fire might occur, so you may want to have some of each. Fortunately dual sensor smoke alarms are available. These contain both ionization and photoelectric sensors.
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