PRODUCT FEATURES:- Photoelectric Smoke Sensing Technology - Electrochemical Carbon Monoxide Sensor - Two AA Battery Operated - Two Silence Features – Silence low battery chirp for up to 8 hours or, temporary silence nuisance alarm conditions - Two Latching Features – Alarm Latch: Remembers and identifies initiating alarms. Low Battery: Identifies affected unit. - Spread Spectrum Horn – Easier for elderly with normal hearing loss to hear - Optipath 360 Technology – Patented photoelectric smoke sensing design - 7-Year Limited Warranty