Mfg # CAT. CO25OB, Carbon Monoxide Alarm, 9V Battert Powered with 2 Silence features; Can temporarily silence the low battery chirp for up to 8 hours or silence an unwanted alarm for several minutes;  Hinged Cover for Easy Battery Replacement; Lighted Power and Alarm Indicator; Tamper Resistant Locking Pin to prevent removal of battery; Perfect for aaprtment, dormitory or hotel applications; Dimensions: 4.25"DIA x1.6"H; Electrochemical CO sensor; End of life signal by providing audible confirmation alarm; Replace alarm 84 months after installation; Recommended battery replacement is Duracell MN1604 and Energizer 522.