features: Carbon Monoxide Detector Battery-operated carbon monoxide (CO) alarm Uses the patented Nighthawk electrochemical CO sensor to help protect you and your family from the dangers of CO. Easy to install, When the detector is operating properly and hazardous CO levels are not detected, its green LED flashes every 30 seconds. In a CO emergency, the red LED pulses and an 85 dB horn sounds at specific intervals until the CO threat is eliminated. Powered by AA batteries, Provide continuous monitoring of CO levels, even during power outages. Battery replacement alarm. Test / reset button A peak-level memory keeps track of the maximum CO level detected between resets. Covered with a 7-year manufacturers limited warranty and replacement is recommended after seven years. Test/reset feature. Loud 85dB alarm. End-of-life warning signal. Approved to BSI (EN50291). 7-year warranty.