▪ Two AA Batteries ▪ Electrochemical Co Sensor ▪ Two Silence Features: Silences Low Battery Chirps For Up To Eight Hours Or Temporarily Silences Nuisance Alarms ▪ Single Test/Silence Button ▪ End-Of-Life Signal (CO) ▪ 7-Year Limited Warranty ▪ Mfg #CO400A