Smoke alarms should be placed in each bedroom and hallway outside the sleeping area. In addition, a detector is required on each level of your home. It is recommended that you change your batteries in your smoke alarms when you change your clocks - twice a year. While changing batteries, also vacuum your detector to prevent dust build-up. You should check your alarms with the test button each month to make sure they alarm properly. Smoke alarms need to be replaced every ten years or sooner if they quit working. The materials used in making the detector lose their effectiveness over time causing the detector to eventually fail.