"Change your clock, change your smoke detector batteries"
That’s a great reminder from the Chicago Fire Department. Everyone knows that a working smoke detector can help save lives in the event of a fire by providing an early warning signal. This is especially critical in buildings made of wood, that have combustible items stored inside, and usually lack sprinkler systems. Fires that last more than four minutes can wipe out the building totally.
There are many different brands of smoke alarms available, but they generally fall into two basic types: ionization and photoelectric. Ionization alarms sound more quickly when a flaming, fast moving fire occurs. Photoelectric alarms are quicker at sensing smoldering, smoky fires.
There are also smoke alarms that combine ionization and photoelectric into one unit, called duel sensor smoke alarms. The U.S. Fire Administration (USFA) recommends the installation of both ionization and photoelectric, or duel sensor smoke alarms.
The USFA reports that most smoke alarms (both hard wired and battery) have a life span of about eight to ten years. After this time, the entire unit should be replaced. Write the date of purchase on the side of the alarm, so you know when to replace it. Some newer alarms have the manufacturing date printed on the inside. It’s important to test all smoke detectors monthly, and replace batteries at least twice a year.