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City Manager's Office
Press Contact: John Fitch, Assistant Fire Chief/ Fire Marshal, (510) 981-5585


Berkeley, California (Friday, October 01, 2010) - Smoke alarms are designed to alert home occupants in the event of a fire.  That is why it is so important to have your smoke alarms mounted in and around your bedrooms so they can be easily heard when you are sleeping.

The Berkeley Fire Department encourages you to check your smoke alarm at least every six months to ensure they are working properly and change the batteries as well. A good way to remember this is when you change your clocks for daylight savings time you should change your smoke alarm batteries. There is a test button on the cover of your smoke alarm that you can press to test the alarm. If you are hearing a chirping sound from your smoke alarm, that may be a sign that your battery is low.  If your smoke alarm is hard wired to the building electrical system it will still normally work, but the battery should be replaced if the unit chirps so that the detector will work even during a power failure.

Statistics have shown that homes with working and serviceable smoke alarms have dramatically decreased the chances of serious injury as a result of home fires.  Home smoke alarms can give false alarms, but generally aren't overly sensitive to cigarette smoke. If a smoke alarm gives frequent false alarms it may need to be moved slightly, changed to a different type of smoke alarm (see below), or replaced with a smoke alarm that has a "hush" button that silences the alarm for ten minutes.


Question:     Where should I put a smoke alarm?

Answer:        In every bedroom and in main hallways on each floor

Question:     When should I change the battery?

Answer:        Every six months if using standard alkaline batteries

Question:     What are the two types of smoke detectors?

Answer:       The two types of smoke detectors are ionization and photoelectric

Question:     Please explain the differences between the two type of smoke alarms.


Ionization smoke detection is generally more responsive to flaming fires: Ionization-type smoke alarms have a small amount of radioactive material between two electrically charged plates, which ionizes the air and causes current to flow between the plates. When smoke enters the chamber, it disrupts the flow of ions, thus reducing the flow of current and activating the alarm.

 Photoelectric smoke detection is generally more responsive to fires that begin with a long period of smoldering (called "smoldering fires"). Photoelectric-type alarms aim a light source into a sensing chamber at an angle away from the sensor. Smoke enters the chamber, reflecting light onto the light sensor; triggering the alarm.

For each type of smoke alarm, the advantage it provides may be critical to life safety in some fire situations. Home fatal fires, day or night, include a large number of smoldering fires and a large number of flaming fires. One cannot predict the type of fire you may have in your home or when it will occur. Any smoke alarm technology, to be acceptable, must perform acceptably for both types of fires in order to provide early warning of fire at all times of the day or night and whether you are asleep or awake.

For best protection, it is recommended both (ionization and photoelectric) technologies be in homes. In addition to individual ionization and photoelectric alarms, combination alarms that include both technologies in a single device are available.

If you should have any additional questions regarding this issue, please do not hesitate to call the Berkeley Fire Department's Fire Prevention Division at (510) 981-5585.


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