First Alert PC910  10-Year 2 in 1 Photoelectric Smoke Detector with Carbon Monoxide Alarm, White Sleek, battery-operated combination smoke and CO alarm detects two potentially deadly threats Photoelectric sensor detects smoke from smoldering fires while minimizing false alarms Electrochemical CO sensor alerts you to carbon monoxide danger from multiple sources Built-in 10-year battery offers continuous power for the life of the alarm Stylish, low-profile design mounts easily on wall or ceiling Complies with all current 10-year legislation in states/cities where required No Battery Changes for the Life of the Alarm; 3V Lithium Power Cell Included Includes Carbon Monoxide Alarm along with the Smoke/Fire Detector all in one unit Patented smoke entry system allows for a direct path to the photoelectric smoke sensor Nuisance free photoelectric technology reduces false alarms that result from cooking and shower steam