Everyone knows you should replace your smoke detector battery every year. But it will probably come as a surprise to learn that you should replace the entire smoke detector every 8 to 10 years. This applies, by the way, to both battery operated and hard-wired models.
To understand why this is necessary, consider that a smoke detector monitors the air constantly 24 hours a day. that means after 10 years a detector has been through, according to some estimates, three to four million duty cycles. So it's no surprise that components can wear out. In addition, detectors can become clogged by dust and other contaminants in the air.
If you're not sure how old your detector is, look on the label (located on the back) for a manufacturing date. To make replacement easy, write the replacement date on that detector or on the new one you install. Then you'll be reminded of its age every year when you change the battery.
Workbench June 2008