Kidde 21006931 FireX Hardwire Smoke Alarm with Battery Backup Change the battery in seconds Front loading battery door; change battery without removing the unit from the bracket Hush feature temporarily silences nuisance alarms One button tests the unit's circuit operation and resets its memory after an alarming condition occurs Kiddes smoke alarms meet the requirements of Underwriters Laboratories (UL), an independent facility that tests products for compliance with widely-accepted safety standards