The Smartwares RM218 10 years sounds the alarm when it detects smoke inside your home. The high-pitched and loud, 85-decibel sound will wake you up immediately. The smoke detector runs on a 3V lithium battery that lasts 10 years. It's mounted to the ceiling with the screws included, somewhere along the escape route. When the battery is empty, the smoke detector will notify you with a beep.