Install reliable fire and carbon monoxide (CO) protection with this First Alert® Value Safety 2 Pack. It includes the SMI100 battery-operated smoke alarm and the CO400 battery-operated carbon monoxide alarm. The SMI100 Smoke Alarm features the First Alert® Precision Detection advanced-sensing technology that meets the latest industry standards to reduce cooking nuisance alarms, detect smoke from synthetic materials, and provide early warning in the event of a home fire emergency. The CO400 carbon monoxide alarm utilizes an electrochemical carbon monoxide sensor - the most accurate sensor available - to detect carbon monoxide. Both are battery operated, easy to install, have convenient test/silence buttons, front-access battery doors for easy battery replacement, and will work in the event of a power outage. | First Alert | | Standard Battery-Operated Smoke and CO Alarm 2 Pack Models SMI100 and CO400 | White | Best Buy