Kidde KN-COB-B Battery-Operated Basic Carbon Monoxide Alarm with Electrochemical Sensor, 1-Pack Battery operated 3 AA's included Front load battery door provides easy access which reduces the installation and battery replacement time Battery lockout system deters closing battery compartment without batteries Test reset button tests the unit for proper operation Kiddes carbon monoxide alarms meet the requirements of Underwriters Laboratories (UL), an independent facility that tests products for compliance with widely-accepted safety standards